The mechanistic and evolutionary basis of stereospecificity for hydrogen transfers in enzyme-catalysed processes

Abstract

The original of stereospecificity in enzylme-catalysed processes is attributed to either mechanistic imperatives or to the evolutionary origin of an enzyme. Recent analysis of the synanti dichotomy for hydratase–dehydratase enzymes has clearly demonstrated that it is a historical contingency that has played a significant role in determination of stereospecificity. Historical contingencies also appear to play a significant role in (a) the selection of one out of a possible eight different stereochemical courses available for an enoyl thioester reductase, and (b) the discrimination between diastereotopic hydrogens in coenzyme B₁₂-dependent rearrangements.