Regulation of two soluble forms of brain glutamate dehydrogenase isoproteins by leucine

Jongweon Lee, Jong Eun Lee, Soo Young Choi, Sung Woo Cho

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Abstract

The stimulatory effects of leucine on the activities of two soluble forms of brain glutamate dehydrogenase isoproteins (GDH I and GDH II) have been studied at various conditions. There were significant differences between GDH I and GDH II in their sensitivities to the action of leucine. When the effects of varied leucine concentrations on GDH activities were studied in the direction of reductive amination of 2-oxoglutarate with NADPH as a coenzyme, a marked activation was observed for both isoproteins at leucine concentrations up to 10 mM. whereas both isoproteins showed activation to a lesser extent with NADH as a coenzyme. The stimulatory effects of leucine on GDH activities in the direction of the oxidative deamination of glutamate were also observed, but to a much lesser extent. Leucine relieved the inhibition of GDH I by GTP and this resulted in an increase in the apparent activation by leucine in the presence of GTP. 2-Oxoglutarate was found to give rise to high substrate inhibition and leucine significantly reduced the substrate inhibition in the presence of 200 μM NADH. Thus, the effects of leucine might be composed of a direct effect on the enzyme together with a relief of high substrate inhibition.

Original languageEnglish
Pages (from-to)332-336
Number of pages5
JournalJournal of biochemistry and molecular biology
Volume30
Issue number5
Publication statusPublished - 1997 Sep 30

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

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