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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5'-Adenylic acid deaminase free from sodium and potassium ion is prepared from erythrocytes by a convenient method. Like adenosine triphosphatase and adenylic kinase from erythrocytes, the deaminase is activated by some monovalent cations, but unlike these enzymes it requires the presence of a monovalent cation. In all three instances the pattern of activation by ions is similar and suggests a common mechanism.
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PMID:Erythrocytes: 5' -adenylic acid deaminase requirement for ammonia or monovalent metal ion. 1396 30

Elevated intracellular calcium generates rapid, profound, and irreversible changes in the nucleotide metabolism of human red blood cells (RBCs), triggered by the adenosine triphosphatase (ATPase) activity of the powerful plasma membrane calcium pump (PMCA). In the absence of glycolytic substrates, Ca(2+)-induced nucleotide changes are thought to be determined by the interaction between PMCA ATPase, adenylate kinase, and AMP-deaminase enzymes, but the extent to which this three-enzyme system can account for the Ca(2+)-induced effects has not been investigated in detail before. Such a study requires the formulation of a model incorporating the known kinetics of the three-enzyme system and a direct comparison between its predictions and precise measurements of the Ca(2+)-induced nucleotide changes, a precision not available from earlier studies. Using state-of-the-art high-performance liquid chromatography, we measured the changes in the RBC contents of ATP, ADP, AMP, and IMP during the first 35 min after ionophore-induced pump-saturating Ca(2+) loads in the absence of glycolytic substrates. Comparison between measured and model-predicted changes revealed that for good fits it was necessary to assume mean ATPase V(max) values much higher than those ever measured by PMCA-mediated Ca(2+) extrusion. These results suggest that the local nucleotide concentrations generated by ATPase activity at the inner membrane surface differed substantially from those measured in bulk cell extracts, supporting previous evidence for the existence of a submembrane microdomain with a distinct nucleotide metabolism.
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PMID:Elevated intracellular Ca2+ reveals a functional membrane nucleotide pool in intact human red blood cells. 2194 47


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