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Free keywords:
enantioselectivity; hydrolysis; stereoselectivity; sulfatases; sulfate esters
Abstract:
The molecular mechanisms of the commonly employed hydrolases involve nucleophilic attack onto the carbonyl group of carboxylic acids or their derivatives.1, 2 As this group is a planar entity, any stereochemical alterations of the substrate caused by enzymatic catalysis are impossible, and as a consequence, enantiomers of the transformed substrate and product are usually homochiral (with the exception of prochiral or meso esters), that is, they have the same absolute configuration. Although the stereochemical features of the substrate, such as stereogenic centers (in racemates) or enantiotopic groups (in prochiral or meso compounds), are “recognized” by the enzyme, which gives rise to differences in kcat and/or KM values, they remain unchanged during catalysis.
Biocatalysts, which elicit the more complex potential to affect the stereochemistry of the substrate in a controlled fashion during catalysis, are rather rare and encompass haloalkane dehalogenases,3 epoxide hydrolases,4 and (alkyl) sulfatases.5, 6 In each case, a C(sp3) atom could potentially be involved in the catalysis and therefore open the possibility of stereocomplementary pathways. These enzymes do not only display enantioselectivity (through the transformation of one substrate enantiomer faster than the other) but also stereoselectivity (with retention or inversion of configuration). This therefore makes them important catalytic tools for the development of so‐called enantioconvergent processes in which each enantiomer from a racemic mixture is transformed into the same product through independent pathways, that is, through retention and inversion of configuration.7 As a consequence, a racemate can be converted, in principle, into a single stereoisomeric product without the occurrence of an undesired stereoisomer.
