Kinetics and stability of Δ5-3-ketosteroid isomerase from Pseudomonas testosteroni in the system of reverse micelles of aerosol OT in isooctane

Abstract Partially purified Δ 5 -3-ketosteroid isomerase (KSI) from Pseudomonas testosteroni was studied kinetically after solubilization in reverse micelles of aerosol OT (AOT) in isooctane and water, as regards its application to biotechnology. With Δ 5,10 -estren-17 β -ol-3-one as a substrate, KSI displays an enzyme activity in the micellar system but a low stability. In the presence of urea, the enzyme is, however, stable. Kinetic parametes of the stabilized enzyme are highly sensitive to both the hydration degree of the surfactant and its concentration. The hypothesis of the geometric correspondence of a non-spherical enzyme and spherical micellar matrix is considered.