Singh K

References (20)

Title : Alkaliphilic and thermostable lipase production by leaf litter fungus Leptosphaerulina trifolii A SMR-2011 - Vasundhara_2024_Arch.Microbiol_206_264
Author(s) : Vasundhara M , Singh K , Suryanarayanan TS , Reddy MS
Ref : Arch Microbiol , 206 :264 , 2024
Abstract : Fungi that inhabit fire-prone forests have to be adapted to harsh conditions and fungi affiliated to Ascomycota recovered from foliar litter samples were used for bioprospecting of molecules such as enzymes. Agni's fungi isolated from leaf litter, whose spores are capable of tolerating 110 (o)C were screened for thermostable lipases. One of the isolates, Leptosphaerulina trifolii A SMR-2011 exhibited high positive lipase activity than other isolates while screening through agar plate assay using Tween 20 in the medium. Maximum lipase activity (173.2 U/mg) of L. trifolii was observed at six days of inoculation and decreased thereafter. Among different oils used, the maximum lipase activity was attained by soybean oil (940.1 U/mg) followed by sunflower oil (917.1 U/mg), and then by mustard oil (884.8 U/mg), showing its specificity towards unsaturated fatty acids. Among the various organic nitrogen sources tested, soybean meal showed maximum lipase activity (985.4 U/mg). The partially purified enzyme was active over a wide range of pH from 8 to 12 with a pH optimum of 11.0 (728.1 U/mg) and a temperature range of 60-80 (o)C with an optimal temperature of 70 (o)C (779.1 U/mg). The results showed that lipase produced by L. trifolii is alkali stable and retained 85% of its activity at pH 11.0. This enzyme also showed high thermal stability retaining more than 50% of activity when incubated at 60 (o)C to 90 degreesC for 2 h. The ions Ca(2+) and Mn(2+) induced the lipase activity, while Cu(2+) and Zn(2+) ions lowered the activity compared to control. These results suggests that the leaf litter fungus L. trifolii serves as a potential source for the production of alkali-tolerant and thermostable lipase.
ESTHER : Vasundhara_2024_Arch.Microbiol_206_264
PubMedSearch : Vasundhara_2024_Arch.Microbiol_206_264
PubMedID: 38760519

Title : A Review of the Common Neurodegenerative Disorders: Current Therapeutic Approaches and the Potential Role of Bioactive Peptides - Singh_2024_Curr.Protein.Pept.Sci__
Author(s) : Singh K , Gupta JK , Kumar S , Soni U
Ref : Curr Protein Pept Sci , : , 2024
Abstract : Neurodegenerative disorders, which include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), represent a significant and growing global health challenge. Current therapies predominantly focus on symptom management rather than altering disease progression. In this review, we discuss the major therapeutic strategies in practice for these disorders, highlighting their limitations. For AD, the mainstay treatments are cholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists. For PD, dopamine replacement therapies, including levodopa, are commonly used. HD is managed primarily with symptomatic treatments, and reusable extends survival in ALS. However, none of these therapies halts or substantially slows the neurodegenerative process. In contrast, this review highlights emerging research into bioactive peptides as potential therapeutic agents. These naturally occurring or synthetically designed molecules can interact with specific cellular targets, potentially modulating disease processes. Preclinical studies suggest that bioactive peptides may mitigate oxidative stress, inflammation, and protein misfolding, which are common pathological features in neurodegenerative diseases. Clinical trials using bioactive peptides for neurodegeneration are limited but show promising initial results. For instance, hemiacetal, a gamma-secretase inhibitor peptide, has shown potential in AD by reducing amyloid-beta production, though its development was discontinued due to side effects. Despite these advancements, many challenges remain, including identifying optimal peptides, confirming their mechanisms of action, and overcoming obstacles related to their delivery to the brain. Future research should prioritize the discovery and development of novel bioactive peptides and improve our understanding of their pharmacokinetics and pharmacodynamics. Ultimately, this approach may lead to more effective therapies for neurodegenerative disorders, moving beyond symptom management to potentially modify the course of these devastating diseases.
ESTHER : Singh_2024_Curr.Protein.Pept.Sci__
PubMedSearch : Singh_2024_Curr.Protein.Pept.Sci__
PubMedID: 38561605

Title : Pathogenesis of Alzheimer's Disease and Diversity of 1,2,3-Triazole Scaffold in Drug Development: Design Strategies, Structural Insights, and Therapeutic Potential - Singh_2023_ACS.Chem.Neurosci__
Author(s) : Singh A , Singh K , Kaur J , Kaur R , Sharma A , Kaur U , Chadha R , Bedi PMS
Ref : ACS Chem Neurosci , : , 2023
Abstract : Alzheimer's disease is a most prevalent form of dementia all around the globe and currently poses a significant challenge to the healthcare system. Currently available drugs only slow the progression of this disease rather than provide proper containment. Identification of multiple targets responsible for this disease in the last three decades established it as a multifactorial neurodegenerative disorder that needs novel multifunctional agents for its management and the possible reason for the failure of currently available single target clinical drugs. 1,2,3-Triazole is a miraculous nucleus in medicinal chemistry and the first choice for development of multifunctional hybrid molecules. Apart from that, it is an integral component of various drugs in clinical trials as well as in clinical practice. This review is focused on the pathogenesis of Alzheimer's disease and 1,2,3-triazole containing derivatives developed in recent decades as potential anti-Alzheimer's agents. The review will provide (A) precise insight of various established targets of Alzheimer's disease including cholinergic, amyloid, tau, monoamine oxidases, glutamate, calcium, and reactive oxygen species hypothesis and (B) design hypothesis, structure-activity relationships, and pharmacological outcomes of 1,2,3-triazole containing multifunctional anti-Alzheimer's agents. This review will provide a baseline for various research groups working on Alzheimer's drug development in designing potent, safer, and effective multifunctional anti-Alzheimer's candidates of the future.
ESTHER : Singh_2023_ACS.Chem.Neurosci__
PubMedSearch : Singh_2023_ACS.Chem.Neurosci__
PubMedID: 37683129

Title : Lysosomal acid lipase, CSF1R and PD-L1 determine functions of CD11c+ myeloid-derived suppressor cells - Zhao_2022_JCI.Insight__
Author(s) : Zhao T , Liu S , Ding X , Johnson EM , Hanna NH , Singh K , Sen CK , Wan J , Du H , Yan C
Ref : JCI Insight , : , 2022
Abstract : Lysosomal acid lipase (LAL) is a key enzyme in the metabolic pathway of neutral lipids. In the blood of LAL deficient (lal-/-) mice, increased CD11c+ cells were accompanied by up-regulated PD-L1 expression. Single cell RNA sequencing of lal-/- CD11c+ cells identified two distinctive clusters with a major metabolic shift towards glucose utilization and reactive oxygen species (ROS) over-production. Pharmacologically blocking pyruvate dehydrogenase in glycolysis not only reduced CD11c+ cells and their PD-L1 expression, but also reversed their capabilities of T cell suppression and tumor growth stimulation. Colony-stimulating factor 1 receptor (CSF1R) plays an essential role in controlling lal-/- CD11c+ cell homeostasis and function and PD-L1 expression. Inhibition of LAL activity by pharmacological inhibitor increased CD11c, PD-L1 and CSF1R levels in both normal murine myeloid cells and human blood cells. Tumor-bearing mice and human non-small-cell lung cancer (NSCLC) patients also showed CD11c+ cell expansion with PD-L1 and CSF1R up-regulation and immunosuppression. There were positive correlations among CD11c, PD-L1 and CSF1R expression and negative correlations with LAL expression in lung cancer and melanoma patients using the TCGA database and patient samples. Therefore, CD11c+ cells switched their functions to immune suppression and tumor growth stimulation through CSF1R/PD-L1 upregulation and metabolic reprogramming.
ESTHER : Zhao_2022_JCI.Insight__
PubMedSearch : Zhao_2022_JCI.Insight__
PubMedID: 35917184

Title : Comparative susceptibility of Rhipicephalus microplus collected from the northern state of India to coumaphos, malathion, deltamethrin, ivermectin, and fipronil - Bisht_2021_Trop.Anim.Health.Prod_53_460
Author(s) : Bisht N , Kumar S , Sharma AK , Nandi A , Singh K , Fular A , Nagar G , Ghosh S
Ref : Trop Anim Health Prod , 53 :460 , 2021
Abstract : The chemical-based tick management method is gradually losing its clutch due to the establishment of resistant ticks. For development of region-specific tick management strategies, the present study was aimed to evaluate the comparative resistance profile of Rhipicephalus microplus isolates collected from seven districts of Uttar Pradesh, a northern state of India. Comparative analysis of the dose-response data using adult immersion test (AIT) against coumaphos, malathion, deltamethrin, ivermectin, and fipronil revealed that all the isolates were resistant to discriminating concentration of deltamethrin having LC(50) of 295.12-436.52 ppm with a resistance ratio of 22.02-32.58. An emerging low level of ivermectin resistance (resistance ratio, RR(50) = 1.03-2.26) with LC(50) in the range of 22.39-48.98 ppm was found across the isolates. The coumaphos was highly effective against all except Amethi (AMT) isolate. Similarly, malathion was efficacious against most of the isolates except Pratapgarh (PRT) and Sultanpur (SUL) isolates showing LC(50) of 5128.61 and 5623.41 ppm, respectively. All the isolates were responsive to fipronil. Comparative detoxifying enzymes profiles revealed a significant correlation between the increased activity of esterase and deltamethrin resistance. The GST activity was 51.2% correlated with RR(50) of malathion while esterase activity was significantly correlated (68.9%) with RR(50) of coumaphos. No correlation between the ivermectin resistance and enzyme activity was established. Multiple sequence analysis of S4-5 linker region of the sodium channel gene of all the isolates revealed a point mutation at 190th position (C190A) which is associated with deltamethrin resistance. The possible tick management strategies in this part of the country are discussed.
ESTHER : Bisht_2021_Trop.Anim.Health.Prod_53_460
PubMedSearch : Bisht_2021_Trop.Anim.Health.Prod_53_460
PubMedID: 34542704

Title : Characterization of deltamethrin, cypermethrin, coumaphos and ivermectin resistance in populations of Rhipicephalus microplus in India and efficacy of an antitick natural formulation prepared from Ageratum conyzoides - Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
Author(s) : Kumar S , Sharma AK , Kumar B , Shakya M , Patel JA , Bisht N , Chigure GM , Singh K , Kumar R , Srivastava S , Rawat P , Ghosh S
Ref : Ticks Tick Borne Dis , 12 :101818 , 2021
Abstract : Rhipicephalus microplus is posing a serious threat to productive animal husbandry. Excessive use of synthetic chemicals in tick management has led to the development of resistant tick populations. Characterization of resistance to deltamethrin, cypermethrin, coumaphos and ivermectin in ticks is necessary to develop a suitable and sustainable control strategy. Based on adult immersion test and larval packet test, the resistance ratios (RR(50)) for adults and larvae of R. microplus populations from two Indian states ranged from 3.8 to 19.4 and 1.35-25.0 against deltamethrin, 0.061-26.3 and 0.22-19.2 against cypermethrin, and 0.2-9.5 and 0.01-3.1 against coumaphos, respectively, were recorded. Moreover, the RR(50) for adults ranged from 0.212 to 3.87 against ivermectin. The RR(50) for different acaricides was significantly (p<0.01) correlated with esterases, Glutathione S-transferase and monooxygenase activity. A point mutation at the 190th position of the domain II S4-5 linker region of the sodium channel gene in synthetic pyrethroids (SP) resistant populations was also detected. An antitick natural formulation prepared from the plant Azeratum conyzoides and containing two major compounds, Precocene-I (7methoxy-2, 2-dimethyl 2H-chromene) and Precocene II (6, 7-dimethoxy-2, 2-dimethyl- 3-chromene), was developed and tested against the resistant ticks. The LC(50) values of the natural formulation against the resistant populations were in the range of 4.31-5.33% irrespective of their RR(50) values. Multi-acaricide resistant populations of R. microplus are established in India and the A. conyzoides based natural formulation can be used for its management.
ESTHER : Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
PubMedSearch : Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
PubMedID: 34537543

Title : Biomarkers for the toxicity of sublethal concentrations of triclosan to the early life stages of carps - Dar_2020_Sci.Rep_10_17322
Author(s) : Dar OI , Sharma S , Singh K , Sharma A , Bhardwaj R , Kaur A
Ref : Sci Rep , 10 :17322 , 2020
Abstract : Accumulation, contents of protein, non-enzymatic antioxidant glutathione (GSH and GSSG), lipid peroxidation product (melondialdehyde-MDA) and organic acids (fumarate, succinate, malate and citrate), and activities of neurological (acetylcholinesterase-AChE), detoxification (glutathione S-transferase-GST) and metabolic (lactate dehydrogenase-LDH, aspartate transaminase-AST and alanine transaminase-ALT) enzymes were recorded in the hatchlings of Cyprinus carpio, Ctenopharyngodon idella, Labeo rohita and Cirrhinus mrigala after 7 and 14 days exposure and 10 days post exposure (recovery period) to sublethal concentrations (0.005, 0.01, 0.02 and 0.05 mg/L) of triclosan, a highly toxic and persistent biocide used in personal care products. Accumulation was maximum between 7-14 days at 0.01 mg/L for C. carpio and L. rohita but at 0.005 mg/L for C. idella and C. mrigala. No triclosan was observed at 0.005 mg/L in C. carpio and C. mrigala after recovery. Significant decline in protein, glutathione and acetylcholinesterase but increase in glutathione S-transferase, lactate dehydrogenase, aspartate transaminase, alanine transaminase, melondialdehyde and organic acids over control during exposure continued till the end of recovery period. Integrated biomarker response (IBR) analysis depicted higher star plot area for glutathione and glutathione S-transferase during initial 7 days of exposure, thereafter, during 7-14 days of exposure and the recovery period, higher star plot area was observed for acetylcholinesterase, aspartate transaminase, alanine transaminase and organic acids. Higher star plot area was observed for protein in all the species throughout the study. The study shows that L. rohita is most sensitive and glutathione, acetylcholinesterase, aspartate transaminase and alanine transaminase are the biomarkers for the toxicity of sublethal concentrations of TCS.
ESTHER : Dar_2020_Sci.Rep_10_17322
PubMedSearch : Dar_2020_Sci.Rep_10_17322
PubMedID: 33057045

Title : Paraoxonase-1 is a better indicator than HDL of Atherosclerosis - A pilot study in North Indian population - Singh_2018_Diabetes.Metab.Syndr_12_275
Author(s) : Singh K , Singh R , Chandra S , Tyagi S
Ref : Diabetes Metab Syndr , 12 :275 , 2018
Abstract : OBJECTIVES: The present study aims to evaluate the levels of HDL and Paraoxonase-1 (PON1) and their correlation in atherosclerotic patients with and without diabetic mellitus (DM) as well as in control subjects in Northern Indian population. MATERIALS AND METHODS: We analyzed lipid profiles and Serum PON1 levels by automated analyzer and ELISA, respectively. Study subjects (N=150) were divided in three groups; Group I: Atherosclerotic patients without DM (N=50), Group II: Atherosclerotic patients with DM (N=50); Group III: Controls (N=50). RESULTS: We found a significantly (p<0.0001) low levels of HDL-C in Group I (32.2+/-7.3) and Group II (36.9+/-11.5) as compared to Group III (41.0+/-7.1). PON-1 levels were also significantly lower in Group I (60.1+/-10.5) and Group II (50.0+/-13.9) when compared to Group III (95.0+/-12.0). We observed a significant correlation (r=0.59, p<0.001) between the levels of PON1 and HDL-C in study subjects. CONCLUSIONS: The reduced levels of HDL and PON-1 and their significant correlation in CAD patients may be associated with the pathogenesis of this disease. Considering HDL as a dependent variable, Paraoxonase-1 is the most important parameter contributing to the total variation in HDL in CAD.
ESTHER : Singh_2018_Diabetes.Metab.Syndr_12_275
PubMedSearch : Singh_2018_Diabetes.Metab.Syndr_12_275
PubMedID: 29254890

Title : mbtJ: an iron stress-induced acetyl hydrolase\/esterase of Mycobacterium tuberculosis helps bacteria to survive during iron stress - Chownk_2018_Future.Microbiol_13_547
Author(s) : Chownk M , Kaur J , Singh K
Ref : Future Microbiol , 13 :547 , 2018
Abstract : AIM: mbtJ from Mycobacterium tuberculosis H37Rv is a member of mbt A-J operon required for mycobactin biogenesis. MATERIALS & METHODS: The esterase/acetyl-hydrolase activity of mbtJ was determined by pNP-esters/native-PAGE and expression under iron stress by quantitative-PCR. Effect of gene on growth/survival of Mycobacterium was studied using antisense. Its effect on morphology, growth/infection was studied in Mycobacterium smegmatis. RESULTS: It showed acetyl hydrolase/esterase activity at pH 8.0 and 50 degrees C with pNP-butyrate. Its expression was upregulated under iron stress. The antisense inhibited the survival of bacterium during iron stress. Expression of mbtJ changed colony morphology and enhanced the growth/infection in M. smegmatis. CONCLUSION: mbtJ, an acetyl-hydrolase/esterase, enhanced the survival of M. tuberculosis under iron stress, affected the growth/infection efficiency in M. smegmatis, suggesting its pivotal role in the intracellular survival of bacterium.
ESTHER : Chownk_2018_Future.Microbiol_13_547
PubMedSearch : Chownk_2018_Future.Microbiol_13_547
PubMedID: 29519132
Gene_locus related to this paper: myctu-Rv2385

Title : mesT, a unique epoxide hydrolase, is essential for optimal growth of Mycobacterium tuberculosis in the presence of styrene oxide - Chownk_2017_Future.Microbiol_12_527
Author(s) : Chownk M , Sharma A , Singh K , Kaur J
Ref : Future Microbiol , 12 :527 , 2017
Abstract : AIM: mesT of Mycobacterium tuberculosis, a hypothetical/putative epoxide hydrolase, is predicted to convert toxic epoxides to the more water-soluble and less toxic diols. Detailed characterization of the protein was carried out.
RESULTS: mesT demonstrated esterase as well as epoxide hydrolase activity. It was membrane bound and was upregulated under hypoxic conditions. The enzyme was able to degrade styrene oxide. The presence of antisense against this gene resulted in the inhibition of in vitro bacterial growth/survival in the presence of styrene oxide. Conclusion & future perspective: We demonstrated that mesT possessed epoxide hydrolase activity and styrene oxide might be its physiological substrate. Inhibition of mesT reduced the growth of the bacteria in presence of styrene oxide and its expression under hypoxic condition suggested its role in intracellular survival of bacteria.
ESTHER : Chownk_2017_Future.Microbiol_12_527
PubMedSearch : Chownk_2017_Future.Microbiol_12_527
PubMedID: 28492351
Gene_locus related to this paper: myctu-LIPS

Title : Microbial degradation of an organophosphate pesticide, malathion - Singh_2014_Crit.Rev.Microbiol_40_146
Author(s) : Singh B , Kaur J , Singh K
Ref : Crit Rev Microbiol , 40 :146 , 2014
Abstract : Abstract Organophosphorus pesticide, malathion, is used in public health, residential, and agricultural settings worldwide to control the pest population. It is proven that exposure to malathion produce toxic effects in humans and other mammals. Due to high toxicity, studies are going on to design effective methods for removal of malathion and its associated compounds from the environment. Among various techniques available, degradation of malathion by microbes proves to be an effective and environment friendly method. Recently, research activities in this area have shown that a diverse range of microorganisms are capable of degrading malathion. Therefore, we aimed at providing an overview of research accomplishments on this subject and discussed the toxicity of malathion and its metabolites, various microorganisms involved in its biodegradation and effect of various environmental parameters on its degradation.
ESTHER : Singh_2014_Crit.Rev.Microbiol_40_146
PubMedSearch : Singh_2014_Crit.Rev.Microbiol_40_146
PubMedID: 23442144

Title : Prognostic significance of estimation of pseudocholinesterase activity and role of pralidoxime therapy in organophosphorous poisoning - Chaudhary_2013_Toxicol.Int_20_214
Author(s) : Chaudhary SC , Singh K , Sawlani KK , Jain N , Vaish AK , Atam V , Patel ML , Agarwal A
Ref : Toxicol Int , 20 :214 , 2013
Abstract : BACKGROUND: Organophosphorous (OP) poisoning is one of the most common poisonings seen in India. OP compounds act through inhibition of enzyme acetylcholinesterase and estimation of pseudocholinesterase (PCE) activity strengthens the diagnosis in clinically uncertain cases of OP poisoning. The role of pralidoxime (PAM) therapy in OP poisoning has been controversial. STUDY OBJECTIVES: This study was aimed to determine the prognostic significance of estimation of PCE activity and also to assess the role of PAM therapy in OP poisoning. MATERIALS AND
METHODS: Patients of suspected OP poisoning of age >12 years admitted to emergency unit at a tertiary healthcare center of north India were enrolled. Patients were categorized into two groups; group A who were given intravenous atropine and group B who were given injectable PAM along with atropine. Serum PCE level was estimated at the time of admission in all patients and severity of OP poisoning was assessed according to PCE level. Requirement of atropine, oxygen inhalation, intubation and ventilatory support, total hospital stay, and mortality were compared between different classes of severity and also between Groups A and B.
RESULTS: This study included a total of 70 subjects, 35 in each group with mean age of 24.99 +/- 8.7 years. Out of 70 subjects 49 (70%) were male and 21 (30%) were female. Forty nine patients (70%) of OP poisoning were with suicidal intent while 21 (30%) cases were accidentally poisoned. In all suicidal cases route of poisoning was ingestion whereas in all the accidental cases route of exposure was inhalational. PCE levels were reduced in all the cases and the mean level was 3,154.16 +/- 2,562.40 IU/L. The total dose of atropine required, need for oxygen inhalation and need for intubation and ventilatory support, mean duration of hospital stay and mortality rate (P = 0.003) were higher in moderate to severe cases and did not have significant difference between Groups A and B. CONCLUSION: The study recommends estimation of PCE level at admission to classify severity of OP poisoning and to estimate prognosis. This study did not find any beneficial role of PAM therapy in reducing morbidity as well as mortality.
ESTHER : Chaudhary_2013_Toxicol.Int_20_214
PubMedSearch : Chaudhary_2013_Toxicol.Int_20_214
PubMedID: 24403730

Title : LipC (Rv0220) is an immunogenic cell surface esterase of Mycobacterium tuberculosis - Shen_2012_Infect.Immun_80_243
Author(s) : Shen G , Singh K , Chandra D , Serveau-Avesque C , Maurin D , Canaan S , Singla R , Behera D , Laal S
Ref : Infect Immun , 80 :243 , 2012
Abstract : We have reported previously the identification of novel proteins of Mycobacterium tuberculosis by the immunoscreening of an expression library of M. tuberculosis genomic DNA with sera obtained from M. tuberculosis-infected rabbits at 5 weeks postinfection. In this study, we report the further characterization of one of these antigens, LipC (Rv0220). LipC is annotated as a member of the Lip family based on the presence of the consensus motif "GXSXG" characteristic of esterases. Although predicted to be a cytoplasmic enzyme, we provide evidence that LipC is a cell surface protein that is present in both the cell wall and the capsule of M. tuberculosis. Consistent with this localization, LipC elicits strong humoral immune responses in both HIV-negative (HIV-) and HIV-positive (HIV+) tuberculosis (TB) patients. The absence of anti-LipC antibodies in sera from purified protein derivative-positive (PPD+) healthy subjects confirms its expression only during active M. tuberculosis infection. Epitope mapping of LipC identified 6 immunodominant epitopes, 5 of which map to the exposed surface of the modeled LipC protein. The recombinant LipC (rLipC) protein also elicits proinflammatory cytokine and chemokine responses from macrophages and pulmonary epithelial cells. rLipC can hydrolyze short-chain esters with the carbon chain containing 2 to 10 carbon atoms. Together, these studies demonstrate that LipC is a novel cell surface-associated esterase of M. tuberculosis that is highly immunogenic and elicits both antibodies and cytokines/chemokines.
ESTHER : Shen_2012_Infect.Immun_80_243
PubMedSearch : Shen_2012_Infect.Immun_80_243
PubMedID: 22038913
Gene_locus related to this paper: myctu-Rv0220

Title : Characterization of a thermostable lipase showing loss of secondary structure at ambient temperature - Sharma_2012_Mol.Biol.Rep_39_2795
Author(s) : Sharma PK , Singh K , Singh R , Capalash N , Ali A , Mohammad O , Kaur J
Ref : Mol Biol Rep , 39 :2795 , 2012
Abstract : A gene encoding extracellular lipase was cloned and characterized from metagenomic DNA extracted from hot spring soil. The recombinant gene was expressed in E. coli and expressed protein was purified to homogeneity using hydrophobic interactions chromatography. The mature polypeptide consists of 388 amino acids with apparent molecular weight of 43 kDa. The enzyme displayed maximum activity at 50 degrees C and pH 9.0. It showed thermal stability up to 40 degrees C without any loss of enzyme activity. Nearly 80% enzyme activity was retained at 50 degrees C even after incubation for 75 min. However above 50 degrees C the enzyme displayed thermal instability. The half life of the enzyme was determined to be 5 min at 60 degrees C. Interestingly the CD spectroscopic study carried out in the temperature range of 25-95 degrees C revealed distortion in solution structure above 35 degrees C. However the intrinsic tryptophan fluorescence spectroscopic study revealed that even with the loss of secondary structure at 35 degrees C and above the tertiary structure was retained. With p-nitrophenyl laurate as a substrate, the enzyme exhibited a K ( m ), V ( max ) and K ( cat ) of 0.73 +/- 0.18 muM, 239 +/- 16 mumol/ml/min and 569 s(-1) respectively. Enzyme activity was strongly inhibited by CuCl(2), HgCl(2) and DEPC but not by PMSF, eserine and SDS. The protein retained significant activity (~70%) with Triton X-100. The enzyme displayed 100% activity in presence of 30% n-Hexane and acetone.
ESTHER : Sharma_2012_Mol.Biol.Rep_39_2795
PubMedSearch : Sharma_2012_Mol.Biol.Rep_39_2795
PubMedID: 21678056

Title : Lipase immobilization on Polysulfone globules and their performances in olive oil hydrolysis - Gupta_2010_Int.J.Biol.Macromol_46_445
Author(s) : Gupta S , Singh K , Bhattacharya A
Ref : Int J Biol Macromol , 46 :445 , 2010
Abstract : We prepared Polysulfone (PS) globules by pouring the PS solution droplets in to the non-solvent water. PS solutions (10, 15, and 20% (w/v), concentrations) of different viscosities resulted different physical appearances in globules. The lipase immobilizing amount (4.32 mg/g) was maximum for PS 20% globules as it possessed maximum BET pore surface area. The olive oil hydrolytic reaction parameters were fitted into the Lineweaver-Burk plot. The K(m) (apparent) values of all the immobilized globules were higher (83.3mM) with respect to free lipases (62.5mM) where as V(max) (apparent) values followed the reverse trend (129.8 U/mg for 20% and 120.5 U/mg for both 15% and 10% PS immobilized globules and 153.8 U/mg for the free lipase respectively). The hydrolytic activity to olive oil was decreased ( approximately 16-20%) after five cycles.
ESTHER : Gupta_2010_Int.J.Biol.Macromol_46_445
PubMedSearch : Gupta_2010_Int.J.Biol.Macromol_46_445
PubMedID: 20138907

Title : Comparative study of performances of lipase immobilized asymmetric polysulfone and polyether sulfone membranes in olive oil hydrolysis - Gupta_2008_Int.J.Biol.Macromol_42_145
Author(s) : Gupta S , Yogesh , Javiya S , Bhambi M , Pundir CS , Singh K , Bhattacharya A
Ref : Int J Biol Macromol , 42 :145 , 2008
Abstract : In the present study, lipase was immobilized via glutaraldehyde crosslinking on the polysulfone and polyether sulfone asymmetric membranes. The results indicated that the overall immobilization of lipase is related to the hydrophobicity of the membrane material and thus higher immobilization is achieved for polysulfone membrane. The evidence of immobilization is done by XRD, SEM, contact angle and porometric studies. Hydrolytic activity of lipase in immobilized form is determined by hydrolyzing olive oil and compared with hydrolytic activity of free lipase. The effect of different reaction parameters viz., temperature, pH, substrate concentration, and incubation time on the lipase activity is investigated. The observed maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) of polysulfone and polyether sulfone is determined.
ESTHER : Gupta_2008_Int.J.Biol.Macromol_42_145
PubMedSearch : Gupta_2008_Int.J.Biol.Macromol_42_145
PubMedID: 18068760

Title : Toxicity to the snail Limnaea acuminata of plant-derived molluscicides in combination with synergists - Singh_2000_Pest.Manag.Sci_56_889
Author(s) : Singh K , Singh D
Ref : Pest Manag Sci , 56 :889 , 2000
Abstract : The effects of combinations of plant-derived molluscicides with piperonyl butoxide (PB) or ENT 8184 (MGK-264) were studied on different enzyme activities and biogenic amine levels in the nervous tissue of Limnaea acuminata. 24-h in vivo exposure of the nervous tissue of L acuminata to 40% and 80% of the 24-h LC50 of the plant-derived molluscicides Azadirachta indica oil, Allium sativum powder and oleoresin of Zingiber officinale rhizome and their active molluscicidal components azadirachtin, allicin and [6]-gingerol, alone or in combination (1 + 5) with PB or ENT 8184, caused a significant reduction in the activity of acetylcholinesterase, lactic dehydrogenase, acid and alkaline phosphatases and sodium-potassium ATPase. There was a significant increase in the activity of succinic dehydrogenase. In vivo exposure for 24-h to sub-lethal concentrations of azadirachtin, allicin and [6]-gingerol, singly and with PB or ENT 8184, significantly altered the dopamine and 5-hydroxytryptamine levels in the nervous tissue of L acuminata. It is concluded that these active moieties singly or with PB or ENT 8184 adversely affect all known neurotransmission mechanisms in the snail, either separately or through a complex interaction between the different neurotransmitters.
ESTHER : Singh_2000_Pest.Manag.Sci_56_889
PubMedSearch : Singh_2000_Pest.Manag.Sci_56_889

Title : The use of piperonyl butoxide and MGK-264 to improve the efficacy of some plant-derived molluscicides - Singh_1998_Pest.Sci_54_145
Author(s) : Singh K , Singh A , Singh DK
Ref : Pest Sci , 54 :145 , 1998
Abstract : Synergism of an oil of Azadirachta indica, a powdered extract of Allium sativum bulbs and an oleoresin of Zingiber officinale rhizomes by piperonyl butoxide and MGK-264 was studied against the snails Lymnaea acuminata and Indoplanorbis exustus. The active components of these plant-derived molluscicides, respectively azadirachtin, allicin and [6]gingerol, were also combined with these synergists. Both piperonyl butoxide and MGK-264 enhanced the toxicity of all of the test compounds. The response of snails to the synergised mixtures was both time- and dose-dependent.
ESTHER : Singh_1998_Pest.Sci_54_145
PubMedSearch : Singh_1998_Pest.Sci_54_145

Title : Studies on the effect of fenbendazole and mebendazole on some enzymes of swine kidney worm Stephanurus dentatus - Singh_1996_Appl.Parasitol_37_217
Author(s) : Singh K , Kaushal P
Ref : Applied Parasitology , 37 :217 , 1996
Abstract : The effect of fenbendazole and mebendazole on the activity of some enzymes of the homogenates of swine kidney worm Stephanurus dentatus was investigated. Fenbendazole at 10(-5) M inhibited malate oxidation by 49% and 51% and oxaloacetate reduction by 33% and 40% whereas, mebendazole at 10(-5) M diminished malate oxidation by 25% and 35% and oxaloacetate reduction by 12% and 14% in male and female S. dentatus, respectively. Lactate dehydrogenase activity was inhibited by 45% and 50% in male and female worm respectively by 10(-5) M fenbendazole. Aldolase activity in both male and female S. dentatus was inhibited by 10(-5) M fenbendazole and mebendazole. Fenbendazole at 10(-5) M caused moderate inhibition of acid and alkaline phosphomonoesterases but mebendazole did not show a significant effect on these enzymes. Cholinesterase activity was not affected significantly with either compound. The possible mode of action of the two compounds is compared.
ESTHER : Singh_1996_Appl.Parasitol_37_217
PubMedSearch : Singh_1996_Appl.Parasitol_37_217
PubMedID: 8856948

Title : Changes in muscarinic binding in distant brain regions showing neuronal losses after folic acid injections into the substantia innominata - Wong_1983_J.Neurochem_40_1754
Author(s) : Wong PT , McGeer EG , Singh K , McGeer PL
Ref : Journal of Neurochemistry , 40 :1754 , 1983
Abstract : Injection of folic acid (FA) into the nucleus substantia innominata (NSI) was found to decrease [3H]quinuclidinyl benzilate ([3H]QNB) binding in the frontal cortex, pyriform cortex, amygdala, and the NSI itself without changing the KD. Binding in the thalamus, caudate nucleus, hippocampus, and substantia nigra was not affected. [3H]Flunitrazepam binding was unchanged in all eight regions studied. Previous work indicates FA injections into the NSI produce epileptiform activity and cause loss of GABAergic and possibly other neurons in the frontal and pyriform cortices, the amygdala, and thalamus. The reductions of [3H]QNB binding in the first three of these regions are interpreted as indicating that many of the neurons lost are cholinoceptive, a finding that supports the previous hypothesis that activation of cholinergic projections from the NSI is an important part of the mechanism of cell loss in these regions.
ESTHER : Wong_1983_J.Neurochem_40_1754
PubMedSearch : Wong_1983_J.Neurochem_40_1754
PubMedID: 6304254