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Studies on the kynurenine adminotransferase activity in rat liver and kidney.

Authors
  • De Antoni, A
  • Costa, C
  • Allegri, G
Type
Published Article
Journal
Hoppe-Seyler's Zeitschrift für physiologische Chemie
Publication Date
Dec 01, 1976
Volume
357
Issue
12
Pages
1707–1712
Identifiers
PMID: 1017797
Source
Medline
License
Unknown

Abstract

The kynurenine aminotransferase activity of supernatant and mitochondrial fractions obtained from rat liver and kidney was studied with L-kynurenine and L-3-hydroxykynurenine as substrates. A substrate inhibition with L-kynurenine at concentrations higher than 6-7mM was observed with all four enzyme preparations. This did not happen with L-3-hydroxykynurenine as a substrate. Moreover, the liver mitochondrial enzyme shows a Km for pyridoxal phosphate 2-4 times smaller than the other preparations when assayed with L-3-hydroxykynurenine as a substrate. Therefore, the accumulation of xanthurenic acid and not of kynurenic acid in B6 deficiency could be related both to this high activity of liver mitochondrial kynurenine aminotransferase with L-3-hydroxykynurenine, even at small concentrations of B6, and to substrate inhibition observed with L-kynurenine and not with L-3-hydroxykynurenine.

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