A carrier enzyme basis for ammonium excretion in teleost gill. NH+4-stimulated Na-dependent ATPase activity in Opsanus beta

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Abstract

1. 1. Branchial Na+ K+-ATPase specific activity is some 20% greater in hyposahne adapted Opsanus beta than in SW specimens. 2. 2. Ouabain insensitive ATPase (Mg2+-ATPase) specific activities were similar, while whole body-activity differences in low salinity and SW adapted fish could be accounted for by the 30% difference in extractable gill protein. 3. 3. NH4+ ion was 15% more effective at dephosphorylation of the microsomal Na-dependent phosphoenzyme than either Rb+ or K+. and revealed a maximal ATPase affinity (Km = 0.2 mM) within the physiological range of blood [K+]. 4. 4. Similar properties as pH optima, ATP and Mg2+ Km's. ouabain sensitivity, percent recoveries and subcell distribution indicated that the NH+4-stimulation acts through the Na+ K+ -ATPase carrier enzyme and may be resonsible for the Na+/NH+4 exchange in Opsanu beta.

Original languageEnglish (US)
Pages (from-to)889-897
Number of pages9
JournalComparative Biochemistry and Physiology -- Part A: Physiology
Volume74
Issue number4
DOIs
StatePublished - 1983

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ASJC Scopus subject areas

  • Physiology

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