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Turnover rates of the canine cardiac Na,K‐ATPases
Author(s) -
Maixent J.M.,
Berrebi-Bertrand I.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80892-x
Subject(s) - atpase , chemistry , medicine , biochemistry , enzyme
Two functional isoforms α (α 1 ) and α + (α 3 ) of the Na,K‐ATPase catalytic subunit coexist in canine cardiac myocytes [J. Biol. Chem. (1987) 262, 8941‐8943]. The in vitro turnover rates of ATP hydrolysis have been determined in sarcolemma preparations by comparing [ 3 H]ouabain‐binding and Na,K‐ATPase activity at various doses of ouabain (0.3–300 nM). The correlation between the occupancy of the ouabain‐binding sites and the degree of Na,K‐ATPase inhibition was not linear. The results showed that the form of low‐affinity for ouabain ( K d = 300–700 nM) exhibited a lower turnover rate (88 ± 10 vs. 147 ± 15 molecules of ATP hydrolyzed per second per ouabain‐binding site) than the high affinity form ( K d = 1–8 nM). Thus our results indicate this specific isoform kinetic difference could contribute to differences in the cardiac cellular function.