engleski

Sucidal Inactivation of B12-dependent Dehydratases – QM//MM Study

Coenzyme B12-dependent diol dehydratase (EC 4.2.1.28) and glycerol dehydratase (EC 4.2.1.30) catalyse the dehydration of 1, 2-diols and glycerol. The dehydration occurs as the first step of the anaerobic fermentation of alcohols in some bacteria. The mechanism of action of these isofunctional and structurally similar enzymes involves the formation of radical intermediates, thanks to the essential cofactor 5’-deoxyadenosylcobalamin (coenzyme B12). Homolytic cleavage of unique cobalt-carbon covalent bond present in coenzyme B12 is responsible for the radical mechanism of catalysis. Both enzymes undergo mechanism based inactivation by their substrate glycerol, the rate of which is higher for diol dehydratase (DDH) than for the glycerol dehydratase (GDH).2 The rate of this suicidal inactivation also depends on the enantiomeric configuration of enzyme-substrate complex. We report the results of a QM/MM study of reactions between glycerol and the B12-dependent dehydratases, DDH and GDH. Energy profiles of enantiomerically different enzyme-substrate complexes are presented and discussed in the context of the mechanism of action and suicidal inactivation.

coenzyme B12; diol dehydratase; glycerol dehydratase; sicudal inactivation

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