Effect of Gallic Acid Polydisulfide on Activity and Stability of Catalase in Various Media

A. N. Eryomin¹, Yu. P. Losev², and D. I. Metelitza^1*

¹Institute 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

²School of Chemistry, Belorussian State University, Leningradskaya ul. 14, Minsk, 220080 Belarus; fax: (0172) 26-5942

^* To whom correspondence should be addressed.

Received June 18, 1998; Revision received June 3, 1999

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The effect of the active bioantioxidant polydisulfide of gallic acid (PDSG) on the catalytic activity and operational and thermal stability of catalase was studied in three media: distilled water (pH ~ 5.6), phosphate buffer, pH 7.4, and reversed micelles of Aerosol OT (AOT) in heptane of varied hydration degree w₀. PDSG inhibited the catalase-induced decomposition of H₂O₂ by the mixed or noncompetitive mechanism: in various media the inactivation constant K_i varied in the range of (0.63-2.32)·10^-5 M. PDSG nearly twofold decreased the rate constant of interaction of the complex I of catalase with H₂O₂ (k₂, M^-1·sec^-1) in water and reversed micelles of AOT and 3-5 times increased the effective rate constant of catalase thermal inactivation, k*_in, sec^-1, depending on the reaction medium. PDSG significantly decreased the rate constant of catalase inactivation during the enzymatic reaction, k_in, sec^-1, and thus increased the enzyme operational stability in water and reversed AOT micelles in heptane. The interaction of PDSG with catalase in water and in phosphate buffer was accompanied by significant changes in CD spectra in the far UV-region that indicated disturbances in the secondary structure of catalase subunits induced by the bioantioxidant; the latter was suggested to initiate the reaction of thiol--disulfide exchange with the enzyme. The problem of the compatibility of catalase with disulfide bioantioxidants is discussed.

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KEY WORDS: catalase, polydisulfide of gallic acid, bioantioxidants, operational stability, thermal stability, reversed micelles, Aerosol OT

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