几种特殊含硫氨基酸对大鼠肝脏胱硫醚-γ-裂解酶的影响。

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

作者信息

Yao K

出版信息

Physiol Chem Phys. 1975;7(5):401-8.

PMID:1197382

Abstract

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 concentrations, more so than cystathionine. DL-alpha-Aminobutyric acid was a weak competitive inhibitor of the homoserine dehydratase, gamma-cystathionase and diaminopropionate ammonia-lyase activities. DL-alpha-Aminopimeric acid has the same chain length as beta-CEC, CMHC and CMTC, but it showed a very weak inhibitory effect compared with the latter sulfur-containing compounds. L-Methionine, DL-methionine sulfoxide, L-ethionine, L-cysteic acid, L-aspartic acid, L-asparagine, L-glutamic acid, L-glutamine, D-alanine, beta-alanine, L-ornithine and L-lysine had little or no effect on any activities of the enzyme preparation. These results were discussed in relation to the catalytic center of cystathionine-gamma-lyase.

摘要

利用本实验室新发现的几种特殊含硫氨基酸，对大鼠肝脏胱硫醚-γ-裂解酶[L-胱硫醚半胱氨酸裂解酶（脱氨基），EC 4.4.1.1]的抑制模式进行了研究。一些半胱氨酸共轭物（CMC、β-CEC、HCETC和HCPC）对高丝氨酸脱水酶和二氨基丙酸氨裂解酶活性均表现出非竞争性抑制，对γ-胱硫醚酶活性表现出竞争性抑制。CMTC对高丝氨酸脱水酶和γ-胱硫醚酶活性均表现出混合型抑制，对二氨基丙酸氨裂解酶活性表现出非竞争性抑制。一些同型半胱氨酸共轭物（CMHC、β-CEHC和HCEHC）对高丝氨酸脱水酶和γ-胱硫醚酶活性均表现出竞争性抑制，对二氨基丙酸氨裂解酶活性表现出混合型抑制。β-CEC、CMHC和β-CEHC也是半胱氨酸脱硫酶活性的有效抑制剂。2. 在测试的其他氨基酸中，DL-同型半胱氨酸和D-半胱氨酸，无论其浓度如何，对高丝氨酸脱水酶活性均表现出混合型抑制。然而，它们在较低浓度下促进γ-胱硫醚酶活性，在较高浓度下抑制该活性，比胱硫醚的抑制作用更强。DL-α-氨基丁酸是高丝氨酸脱水酶、γ-胱硫醚酶和二氨基丙酸氨裂解酶活性的弱竞争性抑制剂。DL-α-氨基庚二酸与β-CEC、CMHC和CMTC具有相同的链长，但与后几种含硫化合物相比，其抑制作用非常弱。L-甲硫氨酸、DL-甲硫氨酸亚砜、L-乙硫氨酸、L-半胱氨酸、L-天冬氨酸、L-天冬酰胺、L-谷氨酸、L-谷氨酰胺、D-丙氨酸、β-丙氨酸、L-鸟氨酸和L-赖氨酸对酶制剂的任何活性几乎没有影响或没有影响。结合胱硫醚-γ-裂解酶的催化中心对这些结果进行了讨论。