Effect of tryptophan metabolites and metal ions on the purified kynureninase from rat liver.
Kynureninase purified from rat liver was inhibited by 3-hydroxyanthranilate, or anthranilate, and slightly by 5-hydroxyanthranilate. However, tryptophan metabolites other than anthranilate and its derivatives, and also alpha-keto acids and alanine did not affect the activity of this enzyme. Kynureninase was also inhibited and inactivated by metal ions, especially Hg2+ and Zn2+. On the other hand Mg2+, Ca2+ and monovalent cations had no effect on the activity of the enzyme. The reductants, such as dithiothreitol, reduced glutathione and mercaptoethanol, prevented this inactivation. p-Chloromercurybenzoate (CMB) and N-ethylmaleimide inhibited the enzyme action. Kynureninase which had been completely inactivated by Hg2+ or CMB could be reactivated with excess dithiothreitol, indicating that enzyme inactivation can be attributed to the blocking of sulfhydryl groups. Five sulfhydryl groups per subunit of the enzyme molecule were detected using CMB and mercury orange.
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006867:Hydrolases; D008099:Liver / Q000201:enzymology*; D008670:Metals / Q000494:pharmacology*; D051381:Rats; D014364:Tryptophan / Q000494:pharmacology*; D062367:ortho-Aminobenzoates / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D008670:Metals; D062367:ortho-Aminobenzoates; D014364:Tryptophan; D006867:Hydrolases; C021480:kynureninase