Mahajan_2019_Int.J.Biol.Macromol_122_806

A priority pollutant Phthalate Esters (PAEs) are widely used as plasticizers and are responsible mainly for carcinogenicity and endocrine disruption in human. For the bioremediation of PAEs, a psychrotolerant Sphingobium yanoikuyae strain P4, capable of utilizing many phthalates dimethyl phthalate (DMP), diethyl phthalate (DEP), dinbutyl phthalate (DBP), diisobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and few Polycyclic Aromatic Hydrocarbons as the sole source of carbon and energy was isolated from Palampur, Kangra, Himachal Pradesh, India. 100% utilization of DBP (1gL(-1)) by the strain was observed within 24h of incubation at 28 degrees C. Interestingly the strain also degraded DBP completely at 20 degrees C and 15 degrees C within 36h and 60h, respectively. Esterase involved in DBP degradation was found to be inducible in nature and intracellular. Comparative sequence analysis of carboxylesterase enzyme sequences revealed conserved motifs: G-X-S-X-G and -HGG- which were the characteristic peptide motifs reported in different esterases. Structural analysis showed that the enzyme belongs to serine hydrolase superfamily, which has an alpha/beta hydrolase fold. Interaction and binding of DBP to a catalytic Ser(184) residue in the esterase enzyme were also analysed. In conclusion, carboxylesterase possess the required active site which may be involved in the catabolism of DBP.