Transfer reactions of acetyl phosphate catalyzed by glyceraldehyde-3-phosphate dehydrogenase.

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidative phosphorylation of acetaldehyde (1) and a number of other aliphatic aldehydes (2, 3) and also has a transacetylating activity (4). In the present paper the reactions of acetyl phosphate which characterize the transacetylating activity of the enzyme are presented. These reactions include (a) the phosphate exchange between acetyl phosphate and radioact,ive inorganic phosphate, (b) t.he arsenolysis of acetyl phosphate, and (c) the acetylation of the thiol groups of coenzyme A (CoA) and glutathione to form X-acetyl CoA and S-acetylglutathione. Although transfer reactions with acetyl phosphate as substrate have not previously been observed to be catalyzed by enzymes from mammalian tissues or yeast, numerous species of bacteria contain a phosphotransacetylase which catalyzes similar reactions (5, 6). The crystalline dehydrogenase differs from the bacterial enzyme in that it cat,alyzes oxidative as well as transfer reactions. Both of the activities of the dehydrogenase may be described by a single reaction mechanism in which an acetyl-enzyme compound is the common intermediate.