Formate Dehydrogenase in a Reversed Micelle System: Regulation of Catalytic Activity and Oligomeric Composition of the Enzyme

N. L. Klyachko,^1,2 S. V. Vakula,¹ V. N. Gladyshev,¹ V. I. Tishkov,¹ and A. V. Levashov¹

¹Department of Chemical Enzymology, School of Chemistry, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-0997.

²To whom correspondence should be addressed.

Submitted July 9, 1997; revision submitted September 12, 1997.

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Formate dehydrogenases from the methylotrophic bacteria Pseudomonas sp. 101 and Mycobacterium vaccae N10 were studied in a system of Aerosol OT reversed micelles in octane. Three peaks of the catalytic activity were found on the plot of activity versus surfactant hydration degree (the size of the micellar inner cavity) which corresponded to functions of the enzyme in various oligomeric forms: monomeric, dimeric, and octameric. Kinetic data were confirmed by results of sedimentation analysis. The enzyme was chemically modified by a bifunctional reagent (dimethyl suberimidate) to obtain a catalytically active non-dissociating dimeric molecule of formate dehydrogenase. In the case of the covalently-linked non-dissociating dimeric enzyme, the peak which corresponded to the monomeric form of the enzyme was found to disappear from the catalytic activity curve.

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KEY WORDS: formate dehydrogenase, catalytically active subunit, regulation of oligomeric composition, reversed micelles, surfactants, Aerosol OT.

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