Hydrogen transfer in catalysis by adenosylcobalamin-dependent diol dehydratase

Studies [bachovchin, W. W., et al. (1978) Biochemistry 17, 2218] of the mechanism of inactivation of adenosylcobalamin-dependent diol dehydratase have led to the development of a general method to describe the kinetics of a reaction pathway containing a reservoir of mobile hydrogen. Analysis by this method of catalytic rate measurements for mixtures of 1,2-propanediol and 1,1-dideuterio-1,2-propanediol supports a mechanism involving an intermediate with three equivalent hydrogens, in which hydrogen transfer from this intermediate to product is the major rate-contributing step. Other results using tritium as a trace label [essenberg, M. K., et al. (1971) J. Am. Chem. Soc. 93, 1242] are considered in light of these deuterium isotope studies.