Formation of 1-deoxy-ketoses by pyruvate dehydrogenase and acetoin dehydrogenase.

Abstract

Cell-free extracts of Bacillus subtilis contain enzyme activities which catalyze an acyloin-type condensation reaction (carboligase reaction) resulting in the formation of l-deoxy-ketoses. The reactions are deduced to proceed as follows: pyruvate+aldose→CO₂+1-deoxy-ketose (I) acetoin+aldose→acetaldehyde+1-deoxy-ketose (II) methylacetoin + aldose→acetone+1-deoxy-ketose (III) Experiments with mutants of B. subtilis defective in pyruvate dehydrogenase (PDH) or acetoin dehydrogenase (AccDH) and with partially purified enzyme preparations revealed that PDH (EC 1.2.4.1) catalyzes reaction (I), and AccDH catalyzes reactions (II) and (III). That the PDH purified from Escherichia coli and the PDC purified from bovine heart also catalyzed reaction (I) indicates that 1 -deoxy-ketose-forming activities are widely distributed. One of the reactions catalyzed by these enzymes is the formation of 1-deoxy-D-threo-pentulose, a precursor of biosynthesis of thiazole ring of thiamine.