Effect of Hydration Degree of Aerosol OT Reversed Micelles and Surfactant Concentration in Heptane on Spectral and Catalytic Properties of Catalase

A. N. Eryomin^* and D. I. Metelitza

Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, ul. Kuprevicha 5/2, Minsk, 220141 Belarus; fax: (0172) 63-7274; E-mail: enzyme@ns.iboch.ac.by

^* To whom correspondence should be addressed.

Received January 22, 1999; Revision received June 7, 1999

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The influence of micelle hydration degree (w₀) and AOT concentration on fluorescence, circular dichroism (CD), catalytic activity, and stability of catalase in Aerosol OT (AOT) reversed micelles in heptane was investigated. The quantitative parameters--differential fluorescence of catalase (DeltaI), protein molar ellipticity ([theta]_lambda), initial rate of catalytic reaction, catalase efficiency (k_cat/K_m), and rate constant of enzyme inactivation (k_in, sec^-1)--decreased with increasing AOT concentration in micellar systems, reflecting the interaction of solubilized catalase with the AOT micellar aggregates in heptane. The dependences of all these parameters on increasing hydration degree of micelles (w₀) were characterized by the appearance of maxima at w₀ of 8, 15-18, and 26-30. These maxima are suggested to reflect three different states of catalase in the micellar system, distinguished by their conformations and catalytic activity, which is determined by the micellar microenvironment of the enzyme.

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KEY WORDS: catalase, reversed micelles, fluorescence, circular dichroism, catalytic activity, stability, proteins in nonaqueous media

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