The function of (Na+K+)ATPase in the β cell: Characterization of the enzyme in a glucose-responsive insulinoma

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Abstract

(Na+K+)ATPase is necessary for the maintenance of the membrane potential. The activity of this enzyme was studied in purified plasma membranes from a glucose-responsive rat insulinoma. Ouabain-sensitive (Na+K+)ATPase activity showed expected ATP dependency with a Km of 0.4 mm. It was also dependent on Mg2+ (Km range 70-80 μM). In the presence of Mg and ATP, half-maximal activity was obtained at a Na concentration of 30 mm and the enzyme activity increased sigmoidally with a Hill coefficient of 1.5. No direct effect on enzyme activity was observed with the insulin secretagogues glucose, fructose, glyceraldehyde, and ketoisocaproate, or with dibuturyl-cAMP and the phosphodiesterase-inhibitor isobutyl methyl xanthine. It is concluded that (Na+K+)ATPase is not directly influenced by known secretagogues associated with insulin release by the β cell.

Original languageEnglish (US)
Pages (from-to)81-85
Number of pages5
JournalBiochemical Medicine and Metabolic Biology
Volume48
Issue number1
DOIs
StatePublished - Aug 1992
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry

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