title: Unsaturation at the surfactant head: influence on the activity of lipase and horseradish peroxidase in reverse micelles.
abstract: Influence of unsaturation present at the surfactant head on the activity of interfacially located enzyme, lipase, and horseradish peroxidase (HRP) is investigated in cationic reverse micelles of a series of surfactants having unsaturated (allyl and pyridinium moieties) as well as analogous saturated (n-propyl and piperidinium moieties) polar head. Lipase activity increases with n-propyl (saturated) substitution as the increase in the headgroup area (A(min)) presumably provides greater space for the enzyme to attain flexible conformation and increases the local concentrations of enzyme and substrate at the interface. In contrast, activity of lipase decreases with increasing number of allyl (unsaturated) substitution though A(min) gradually increased. Similar trend in deactivation was observed when unsaturation is present in cyclic ring (pyridine) at the surfactant head in comparison to the saturated analogue, piperidine. Circular dichroism (CD) spectra of lipase in reverse micelles indicate that ellipticity in the far-UV region increases with increasing unsaturation. Thus, lipase probably loses its alpha-helix content and thereby its activity. Inhibition of biocatalyst with increasing unsaturation at the polar head of surfactant is also observed in case of HRP, an oxidoreductase enzyme.
authors.affiliation: Department of Biological Chemistry and Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
authors.forename: Sisir
authors.initials: S
authors.lastname: Debnath
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Das
authors.forename: Prasanta Kumar
authors.initials: PK
authors.lastname: Das
mesh_terms: D002942:Circular Dichroism; D006735:Horseradish Peroxidase / Q000737:chemistry*; D007700:Kinetics; D008049:Lipase / Q000737:chemistry*; D008823:Micelles; D008968:Molecular Conformation; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry; D013379:Substrate Specificity; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D008823:Micelles; D011725:Pyridines; D013501:Surface-Active Agents; D006735:Horseradish Peroxidase; D008049:Lipase; C023666:pyridine