On Kynureninase Activity

In 1952, Yahito Kotake et al. reported that xanthurenic acid (XA) might be a diabetogenic agent in vitamin B6 (B6)-deficient rats. From that time, many studies have been performed in B6-deficient rats and in diabetic (DM) patients. The results are as follows: 1) The pyridoxal phosphate/pyridoxal ratio in plasma decreased in DM patients compared with the control group [DM group: 0.54 (N = 9); control group: 3.84 (N = 8)], suggesting that pyridoxal kinase activity may be inhibited in DM patients (Hattori et al., 1984).