Hydrophobic binding is not an independent stereochemical determinant in the yeast glyoxalase I reaction

For yeast glyoxalase I, a stereospecific proton-transfer mechanism requires the formation of either a cis or a trans-enediol intermediate. Analogs of the two possible isomeric enediol intermediates, formed from the hemimercaptal due to phenylglyoxal and glutathione, have been synthesized in which the oxygen atoms of the enediol are replaced by protons. Both isomeric analogs are strong linear competitive inhibitors of the enzyme having nearly equal inhibition constants: K_i(cis) = 0.10 mM;K_i(trans) = 0.16 mM. This suggests that while hydrophobic interactions between substrate, enediol intermediate and enzyme may contribute significantly to binding, this type of interaction is not an independent stereochemical determinant of the reaction.