Abstract
Rabbit muscle phosphoglycerate kinase (EC 2.7.2.3) has been phosphorylated with γ-32P-ATP and then isolated by gel filtration. Phosphorylation was favored by the presence of phosphoenolpyruvate and a catalytic amount of pyruvate kinase, which appeared to remove ADP from the phosphorylation equilibrium. The phosphoenzyme was catalytically active, transferring its phosphoryl group to ADP to synthesize ATP. The phosphoenzyme also transferred its phosphoryl group to 3-phosphoglycerate to form 1,3-diphosphoglycerate, which, being unstable, was not isolated. It was converted instead to the corresponding hydroxamate or transformed enzymatically to fructose 1,6-diphosphate. Inorganic phosphate was released from the phosphoenzyme by neutral hydroxylamine at room temperature within 10 min. The pH stability profile of the phosphoenzyme is U-shaped. These facts accord with a covalent binding of the phosphoryl group to a carboxyl of the enzyme.
Highlights
The phosphoenzyme was catalytically active, transferring its phosphoryl group to ADP to synthesize ATP
Phosphorylation was favored by the presence of phosphoenolpyruvate and a catalytic amount of pyruvate kinase, which appeared to remove ADP from the phosphorylation equilibrium
We find that phosphorylated phosphoglycerate kinase can be made by incubating the enzyme with an excess of ATP in the presence of phosphoenolpyruvate and a small quantity of pyruvate kinase
Summary
Phosphoglycerate kinase was isolated and crystallized from yeast by Biicher in 1947 (1). It was the first carboxylate kinase to be recognized.’. It catalyzes one of the prominent ATP-producing reactions of cell metabolism. + ATP F) 1,3-diphosphoglycerate + ADP (1). The same reaction bears a conspicuous part in the carbon reduction cycle of photosynthesis. For these reasons among others, the mode of action of phosphoglycerate kinase has over the years stirred the intermittent interest of investigators (3, 4). Through the use of l*O it was early established that Reaction 1 represents the reversible transfer of a phosphoryl group between ADP and 3-phosphoglycera.te (5, 6).
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