METABOLIC CONTROL AND STRUCTURE OF GLYCOLYTIC ENZYMES .7. DESTABILIZATION AND INACTIVATION OF YEAST GLYCERALDEHYDE 3-PHOSPHATE DEHYDROGENASE BY ADENOSINE PHOSPHATES AND CHYMOTRYPSIN

Yeast glyceraldehyde 3-phosphate dehydrogenase, in the presence of adenosine triphosphate, experiences (1) instantaneous competitive inhibition and (2) slow dissociation into monomers or dimers, Adenosine triphosphate and certain other adenine-containing compounds have now been shown to markedly increase the susceptibility of glyceraldehyde 3-phosphate dehydrogenase to rapid proteolysis by chymotrypsin. Native glyceraldehyde 3-phosphate dehydrogenase lost only a little activity after 7 hr at 25°. In the presence of 1 mM adenosine triphosphate or adenosine diphosphate, the loss of activity was much greater; with adenosine 5′-monophosphate it was only moderate. In sharp contrast, in the presence of adenine, or adenosine, or adenosine 3′5′-cyclic monophosphate, the loss was even less than that of the control with no added nucleotide. Chymotrypsin, in the absence of nucleotides, decreased the activity of glyceraldehyde 3-phosphate dehydrogenase to 87% of its original value in 10 min at 25°. However, in the presence of 1 mM concentrations of adenosine 5′-monophosphate, or adenosine diphosphate, or adenosine triphosphate, chymotrypsin decreased the activity of glyceraldehyde 3-phosphate dehydrogenase to only 37,27, or 10%, respectively, of its original value. Nicotinamide-adenine dinucleotide prevented completely the adenosine triphosphate effect, and adenosine 3′5′-cyclic monophosphate prevented it almost completely. Free terminal phosphate groups, especially terminal pyrophosphate groups, apparently cause the destabilization and increased susceptibility to proteolysis. Two general mechanisms, a feedback inactivation mechanism and a product inactivation mechanism, are proposed for metabolic control of enzyme degradation by the combined action of metabolites and cellular proteolytic enzymes. © 1969, American Chemical Society. All rights reserved.