Title : Effect of counterions on the activity of lipase in cationic water-in-oil microemulsions - Debnath_2006_Langmuir_22_8732
Author(s) : Debnath S , Dasgupta A , Mitra RN , Das PK
Ref : Langmuir , 22 :8732 , 2006
Abstract :

This paper delineates how the different counterions affect the physicochemical properties of the aqueous aggregates and thereby the lipase activities at the interface of cationic water-in-oil microemulsions. To this end, we have synthesized a series of cetyltrimethylammonium-based surfactants, 1-14, having aliphatic, aliphatic with aromatic substitution at the alpha position, and aromatic carboxylate anion as the counterion. The physicochemical characterizations of these aqueous aggregates were done by conductometric, tensiometric, fluorometric techniques to determine counterion binding (beta), critical micelle concentration (cmc), and micropolarity at the microenvironment. It has been found that the activity of lipase mainly increases with hydrophobicity (which is directly proportional to the counterion binding (beta) of the surfactant) of the counterion and reaches a maximum when the beta value is around 0.5. Increase in hydrophobicity as well as beta leads to the attachment of more counterions at interface resulting in enhancement of interfacial area. Consequently, the enzyme may attain flexible secondary conformation at the augmented surface area and also allow larger population of substrates and enzyme molecules at the interface leading to the enhancement in lipase activity. After an optimum value of beta, further increase probably produces a steric crowding at the interface, hindering the smooth occupancy of enzyme and the substrate in this region leading to decrease of enzyme activity, while molecular surface area of the counterion did not show any virtual influence on the lipase activity. Thus, the variation in the counterion structure and hydrophobicity plays a crucial role in modulating the lipase activity.

PubMedSearch : Debnath_2006_Langmuir_22_8732
PubMedID: 17014111

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Citations formats

Debnath S, Dasgupta A, Mitra RN, Das PK (2006)
Effect of counterions on the activity of lipase in cationic water-in-oil microemulsions
Langmuir 22 :8732

Debnath S, Dasgupta A, Mitra RN, Das PK (2006)
Langmuir 22 :8732