Reversible Dissociation of Yeast Glyceraldehyde 3-Phosphate Dehydrogenase by Adenosine Triphosphate

Tetrameric yeast glyceraldehyde 3-phosphate dehydrogenase undergoes a time-dependent inactivation in the presence of adenosine 5′-triphosphate as a result of dissociation into monomeric subunits. Optimal conditions, which yield complete inactivation in 5 hr are: (1) 1-2 mM adenosine 5′-triphosphate, (2) 0°, (3) protein concentrations of 0.03-0.1 mg/ml, (4) pH 9.0, and (5) 0.1 M β-mercaptoethanol. Transition points (half-maximal loss of activity in 5 hr) are: (1) 0.5 mM adenosine 5′-triphosphate, (2) 12°, (3) 0.5 mg/ml, and (4) pH 8.6. Adenosine 5′-monophosphate and adenosine 3′,5′- monophosphate do not dissociate the enzyme. They, and all the substrates of the reaction, partially protect the enzyme from dissociation. Dissociation and inactivation are completely reversed by warming to 17°. Reassembly is greatly stimulated by adenosine 5′-triphosphate and by 10% sucrose. Optimal reassembly conditions are: (1) 0.04 mg/ml of protein, (2) pH 7.0, (3) 1-2 mM adenosine 5′-triphosphate, (4) 17°, (5) 10% sucrose, and (6) 0.1 M β-mercaptoethanol. Inactivation and dissociation apparently result from electrostatic repulsion. The results are discussed in terms of a possible role for this enzyme in the regulation of glycolysis. Since this dissociation produces fairly compact subunits, association of folded monomers to tetramers may be studied independently of the polypeptide folding.