title: Pyruvate kinase-catalyzed ATP-formation in human red blood cell membranes.
abstract: Previous studies on the linkage between enzymatically catalyzed ATP-generating reactions in the red blood cell membrane and the sodium and potassium transport in the control of overall glycolysis of human erythrocytes were controversial. In this study a significant amount of pyruvate kinase activity is shown to be localized within the membrane. Membrane fragments produce 20.5 mumol of ATP per 10(10) membranes per hour from phosphoenolpyruvate and ADP. The kinetics of the membrane-localized pyruvate kinase do not differ from those of the enzyme from hemolysates. The results clearly document the presence of the second ATP-generating enzyme of glycolysis, pyruvate kinase, in human red blood cell membranes. The main fraction of the enzyme is deeply hidden in the lipid layers of the membrane. It can be demasked by mechanical desintegration of membranes at high levels of activity. It is suggested that the amount of the membrane-localized fraction of pyruvate kinase is related to the clinical severity of the hemolytic process in pyruvate kinase deficiency.
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D004910:Erythrocyte Membrane / Q000201:enzymology / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D011770:Pyruvate Kinase / Q000172:deficiency
chemical_list: D000255:Adenosine Triphosphate; D011770:Pyruvate Kinase