Subunit separation in reversed micelle system reveals the existence of active centers both on light and heavy γ‐glutamyltransferase subunits

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Abstract
Regulation of supra‐macromolecular composition and catalytic activity of a heterodimeric enzyme, γ‐glutamyltransferase, in the system of Aerosol OT (sodium bis(2‐ethylhexyl) sulfosuccinate) reversed micelles in octane were studied. Variation of the surfactant hydration degree (parameter, determining dimensions of the polar inner cavity of the micelle) causes a reversible dissociation of the enzyme to light and heavy subunits. Both enzyme subunits possess catalytic activity. The light and heavy subunits of the enzyme were separated on a preparative scale in a reversed micelle system using ultracentrifugation. The active centers of γ‐glutamyltransferase were studied using its irreversible inhibitor — AT‐125 (L·(αS.5S)‐α‐amino‐3‐chloro‐4,5‐dihydro‐5‐isoxazoleacetic acid). Separation of the γ‐glutamyltransferase subunits results in the ‘opening’ of a new active center located at the heavy subunit. In the dimer form of the enzyme this center is masked and it is not accessible to both substrate and inhibitor molecules.

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