Interaction between Adenine Nucleotides and 3-Phosphoglyceraldehyde Dehydrogenase

Abstract

Abstract The interaction of 3-phosphoglyceraldehyde dehydrogenase with various adenine nucleotides has been studied in order to gain insight into the manner in which the coenzyme, NAD, is bound to the enzyme and how this binding affects the various catalytic activities of the protein. The effects of adenine nucleotides were examined on the enzymatic hydrolysis of p-nitrophenyl acetate. This reaction provides a simple model for the formation and turnover of the normally occurring S-acyl-enzyme complex. 5'-AMP, ADP, and ATP stimulated the initial rate of formation of the S-acetyl-enzyme intermediate, but adenosine 3',5'-monophosphate and ADP-ribose had no effect. All adenine nucleotides inhibited the hydrolysis of the S-acetyl-enzyme intermediate with the following order of potency: ADP g ADP-ribose g ATP g 5'-AMP g adenosine 3',5'-monophosphate. By contrast, NAD inhibited the acetylation of the enzyme, and, under certain conditions, facilitated the deacetylation of the S-acetyl intermediate. Adenosine had no effect on the esterase activity. Inorganic pyrophosphate reduced the rate of both the acetylation and deacetylation steps, thereby localizing the inhibitory moiety of the adenine nucleotides. The relationship of these effects to the mechanism of coenzyme binding and enzymatic catalysis is considered.