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Antagonistic effect of urea on oxygenation-linked binding of ATP in an elasmobranch hemoglobin

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  • Roy E. Weber
  • R M Wells, University of Auckland, New Zealand
  • S Tougaard, Danmark
The O2 affinity of "stripped" (cofactor-free) hemoglobin (Hb) of the elasmobranch, Squalus acanthias is decreased by ATP, the main erythrocytic phosphate cofactor but increased by urea at physiological concentration. When both compounds are present, as in life, urea decreases the ATP sensitivity, indicating that previous Hb oxygenation studies in the absence of urea overestimate the modulator role of phosphate cofactors in sharks. Whereas ATP decreases the O2 association equilibrium constant of the deoxygenated pigment, urea raises those of both the deoxy and the oxygenated states. Possible mechanisms for the urea-protein interactions i.e. binding at carboxy-termini or carbamylation of amino-termini of the protein chains, are discussed.
OriginalsprogEngelsk
TidsskriftLife Sciences
Vol/bind32
Nummer18
Sider (fra-til)2157-61
Antal sider5
ISSN0024-3205
StatusUdgivet - 1983

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