Abstract
In contrast to the well-known strict stereo-specificity ascertained in the other vitamin B_<12> coenzyme-dependent reactions involving a hydrogen shift, such as the mutation of L-glutamate to L-threo-β-methylaspartate or of succinyl-CoA to L-methyl malonyl-CoA, comparison has not yet been made between the reactivities of D (-)-propanediol and of its L(+)-isomer. This paper showed that both the isomers could be converted to propionaldehyde, but the D-isomer was 1.5 to 2 times reactive than its L-isomer. An inhibtiion of the reactivity was observed if a high concentration of the L-form or the DL-form was used as a substrate. It appears interesting that the simultaneous addition of the L-form depressed the reactivity of the D-form. Presumptive mechanisms on the interaction between the stereoisomeric substrate and the enzyme are discussed.
