Homocystinuria as Affected by Pyridoxine,Folic Acid,and Vitamin B 12 ∗

Abstract

Summary and Conclusions

Administration of pyridoxine to the four children with homocystinuria who had been on a diet low in pyridoxine resulted in ablation of a general but slight aminoaciduria and a striking reduction in homocystine excretion. Further studies on two of the children showed increases in serum oxalacetic-glutamic transaminase and reduction in xanthurenic acid excretion after tryptophane loading. The marked decrease in homocystine excretion after pyridoxine administration was correlated with increased excretion of inorganic sulfate. The total lack of activity for cystathionine synthetase in liver biopsy tissue after pyridoxine administration to the children even when pyridoxal phosphate was added to the enzyme assay system, lead to the conclusion that the metabolism of methionine sulfur to inorganic sulfate must have been increased through one of the alternate pathways of metabolism. Administration of vitamin B₁₂ and folic acid resulted in a decrease of excretion of homocystine though not as marked as the effects of pyridoxine.