The study of active sites of γ-glutamyltransferase in the system of aerosol OT reversed micelles in octane by the inhibitor method

S. N. Nametkin, A. V. Kabanov, A. V. Levashov

Department of Chemical Enzymology, M. V. Lomonosov Moscow State University

Abstract: Regulation of the supramolecular structure and catalytic activity of the heterodi-meric enzyme γ-glutamyltransferase in the system of Aerosol OT reversed micelles in octane was studied. Variation of the hydration degree causes a reversible dissociation of the enzyme to the light and heavy subunits, both possessing the catalytic activity. The subunits were separated on the preparative scale in the reversed micelle system using ultracentrifugation. The active centres of γ-glutamyltransferase were studied using the enzyme's irreversible inhibitor AT-125 (L-(αS, 5S)-α-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid). It is shown that the separation of the γ-glutamyltransferase subunits results in «opening» of a new active centre in the heavy subunit, whereas in the enzyme's dimeric form this centre is masked and not accessible to the inhibitor's molecule. The kinetic and inhibitor analysis data indicate that the active centres in the light and heavy subunits are similar.

Russian Journal of Bioorganic Chemistry 1991, 17 (8):1027-1032

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