Variations in the kinetic response of several different phosphate-dependent glutaminase isozymes during acute metabolic acidosis

Paloma Hortelano, Leticia García-Salguero, George A O Alleyne, Jose A. Lupiáñez

Research output: Contribution to journalArticlepeer-review

Abstract

We describe the kinetic modifications to mitochondrial-membrane-bound phosphate-dependent glutaminase in various types of rat tissue brought about by acute metabolic acidosis. The activity response of phosphate-dependent glutaminase to glutamine was sigmoidal, showing positive co-operativity, the Hill coefficients always being higher than 2. The enzyme from acidotic rats showed increased activity at subsaturating concentrations of glutamine in kidney tubules, as might be expected, but not in brain, intestine or liver tissues. Nevertheless, when brain and intestine from control rats were incubated in plasma from acutely acidotic rats enzyme activity increased at 1 mM glutamine in the same way as in kidney cortex. The enzyme from liver tissue remained unaltered. S0.5 and nH values decreased significantly in kidney tubules, enterocytes and brain slices preincubated in plasma from acidotic rats. The sigmoidal curves of phosphate-dependent glutaminase shifted to the left without any significant changes in Vmax. The similar response of phosphate-dependent glutaminase to acute acidosis in the kidney, brain and intestine confirms the fact that enzymes from these tissues are kinetically identical and reaffirms the presence of an ammoniagenic factor in plasma, either produced or concentrated in the kidneys of rats with acute acidosis.

Original languageEnglish (US)
Pages (from-to)113-123
Number of pages11
JournalMolecular and Cellular Biochemistry
Volume108
Issue number2
DOIs
StatePublished - Dec 1991
Externally publishedYes

Keywords

  • acute metabolic acidosis
  • brain tissue
  • enterocytes
  • hepatocytes
  • kidney tubules
  • kinetics
  • phosphate-dependent glutaminase

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Clinical Biochemistry
  • Cell Biology

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