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  • Title: Subunit separation in reversed micelle system reveals the existence of active centers both on light and heavy gamma-glutamyltransferase subunits.
    Author: Kabanov AV, Nametkin SN, Chernov NN, Klyachko NL, Levashov AV.
    Journal: FEBS Lett; 1991 Dec 16; 295(1-3):73-6. PubMed ID: 1684940.
    Abstract:
    Regulation of supra-macromolecular composition and catalytic activity of a heterodimeric enzyme, gamma-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 gamma-glutamyltransferase were studied using its irreversible inhibitor--AT-125 (L-(alpha S, 5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid). Separation of the gamma-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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