PMID: 1197382Jan 1, 1975Paper

Effects of several unusual sulfur-containing amino acids on rat liver cystathionine-gamma-lyase

Physiological Chemistry and Physics
K Yao

Abstract

1. The mode of inhibition of rat liver cystathionine-gamma-lyase [L-cystathionine cysteine-lyase (deaminating), EC 4.4.1.1] was studied by using several unusual sulfur-containing amino acids newly found in this laboratory. Some cysteine conjugates (CMC, Beta-CEC, HCETC and HCPC) inhibited noncompetitively both homoserine dehydratase and diaminopropionate ammonia-lyase activities, and competitively gamma-cystathionase activity. CMTC exhibited a mixed type inhibition on both homoserine dehydratase and gamma-cystathionase activities, and a noncompetitive inhibition on the diaminopropionate ammonia-lyase activity. Some homocysteine conjugates (CMHC, beta-CEHC and HCEHC) inhibited competitively both the activity of homoserine dehydratase and of gamma-cystathionase, and exhibited a mixed type inhibition on the diaminopropionate ammonia-lyase activity. beta-CEC, CMHC and beta-CEHC were also effective inhibitors to cysteine desulfhydrase activity. 2. Among the other amino acids tested, DL-homocysteine and D-cysteine, irrespective of their concentration, exhibited a mixed type inhibition on the homoserine dehydratase activity. However, they promoted gamma-cystathionase activity at their lower concentrations and inhibited at their higher...Continue Reading

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