Taurine and Kynureninase
Kynureninase is the most important enzyme in tryptophan metabolism. In the main pathway of tryptophan metabolism, kynureninase forms 3-OH-anthranilic acid from 3-OH-kynurenine. In this reaction vitamin B6 is a co-enzyme. An important relationship between -SH groups and liver kynureninase apoenzyme has been reported by Takeuchi8, 9 and Izuta1. We have experimented on kynureninase and S-involved compounds as follows: (i) Kynureninase activity was inhibited in vitamin B6-deficient rats and in streptozotocin (STZ)-induced diabetic rats; (ii) Following tryptophan administration, in rats given taurine or oysters (rich in taurine), the excretion of xanthurenic acid (an index of vitamin B6 deficiency) decreased compared with an excess methionine-administered group; and (iii) The active center of kynureninase apoenzyme (464 amino acid residues) is located near cysteine.
KeywordsZinc Cysteine Serine Lysine Tryptophan
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