[Substrate specificity of adenosylcobalamin-dependent glycerol dehydratase. Interaction with enantiomers of 1,2-propanediol].

Adenosylcobalamin-dependent glycerol dehydratase was shown to catalyze the conversion of both enantiomers of 1.2-propanediol. The kinetic constants for the dehydration reaction of (R)- and (S)-1.2-propanediol appear to be different. The enzyme preferentially binds 1.2-propanediol in the (S)-configuration; however, the rate of (S)-1,2-propanediol dehydration is 2 times less than that of (R)-1.2-propanediol. The catalytic conversion of 1.2-propanediol enantiomers is accompanied by the enzyme inactivation. During dehydration of (R)-1.2-propanediol the enzyme is inactivated at a higher rate than during the (S)-enantiomer dehydration. The turnover number of the enzyme calculated as a ratio of the rate constants of catalysis and inactivation does not practically depend on the substrate configuration. Consequently, the changes in the configuration of the substrate, 1.2-propanediol, similarly affect the rate-limiting steps of the catalytic and inactivation processes. It is assumed that the (R)- and (S)-enantiomers of 1.2-propanediol are bound at the substrate site of glycerol dehydratase by three identical points.