Formation of Adenosine Triphosphate by a Membrane Fraction from Human Erythrocytes.

Abstract

The enzyme activities of glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase were determined in various fractions during preparation of a membrane fraction from human erythrocytes. The formation of ATP by the purified membrane fraction was also studied. The glyceraldehyde-3-phosphate dehydrogenase was firmly attached to the membranous structure, and the concentration of this enzyme per mg N in the exhaustively washed membrane fraction was 4 times that in the hemolysate. The phosphogylcerate kinase activity in the membrane fraction was 1/10 that of the glyceraldehyde-3-phosphate dehydrogenase. Practically no difference was found between the activity of these 2 enzymes in the hemolysate. The membrane fraction incorporated labeled orthophosphate into ATP is all phosphorylated substrates and cofactors in the glyceral-dehyde-3-phosphate dehydrogenase and phosphoglycerate kinase reactions were present in the medium. The incorporation of labeled orthophosphate into 2,3-diphosphoglyceric acid by the membrane fraction was small in comparison to that into ATP. A considerable amount of ATP was formed in an additional way. It is suggested that it is through the adenylate kinase reaction.