Abstract
It is difficult to explain the excretion of the elevated amounts of xanthurenic acid in vitamin B6 deficient animals with the difference of Km values for pyridoxal phosphate between kynurenine-transaminase and kynureninase.
Kynurenine-transaminase is distributed in mitochondrial and soluble supernatant fractions, while kynureninase only in soluble fraction.
In vitamin B6 deficient rats and in penicillamine administered rats, kynureninase and the supernatant kynurenine-transaminase show markedly decreased activities, while the mitochondrial kynurenine-transaminase remains to be active. A possible explanation for the increased excretion of xanthurenic acid in vitamin B6 deficient rat is presented in view of these findings. The authors wish to thank Dr. N. Katsunuma for his helpful discussion.
