STEREOCHEMISTRY OF THE FORMATION OF LACTALDEHYDE AND ACETOIN PRODUCED BY THE PYRUVATE DECARBOXYLASES OF YEAST (SACCHAROMYCES SP) AND ZYMOMONAS-MOBILIS - DIFFERENT BOLTZMANN DISTRIBUTIONS BETWEEN BOUND FORMS OF THE ELECTROPHILE, ACETALDEHYDE, IN THE 2 ENZYMATIC-REACTIONS

Pyruvate decarboxylase from Saccharomyces sp. catalysed the formation of acetoin of predominantly the opposite configuration than that obtained using the enzyme from Zymomonas mobilis. A similar result was obtained for the lactaldehyde formed in the pyruvate decarboxylase-catalysed decarboxylation of glyoxylate in the presence of acetaldehyde. The results are interpreted in terms of different Boltzmann distributions for the two enzymes between the enzyme-substrate complexes of acetaldehyde bound on its re and si faces respectively.