ENZYMATIC-ACTIVITIES OF RAT-LIVER CYTOSOL 10-FORMYLTETRAHYDROFOLATE DEHYDROGENASE
ENZYMATIC-ACTIVITIES OF RAT-LIVER CYTOSOL 10-FORMYLTETRAHYDROFOLATE DEHYDROGENASE
复制标题
DOI：
10.1006/abbi.1995.1403
复制
发表时间：
1995-08-20
影响因子：
3.9
通讯作者：
WAGNER, C
中科院分区：
文献类型：
--
作者：
COOK, RJ;WAGNER, C
10-甲酰基四氢叶酸脱氢酶（10-FTHFDH：EC www.example.com）催化10-甲酰基四氢叶酸（10-HCO-H（4）PteGlu）的NADP（+）依赖性氧化为四氢叶酸（H（4）PteGlu）和CO2，以及催化10-HCO-H（4）PteGlu的NADP（+）非依赖性水解裂解为H（4）PteGlu和甲酸盐，10-FTHFDH在C-末端具有485个氨基酸的结构域，其与醛脱氢酶（ALDH：EC www.example.com）具有46%的同一性，并含有保守的活性位点半胱氨酸（Cys-707）。10-FTHFDH以与ALDH类似的方式催化丙醛的NADP（+）依赖性氧化和乙酸对硝基苯酯（pNPA）的水解。初始速率研究给出NADP（+）和丙醛的Km值分别为46和636 μ M，而pNPA的Km值为220 μ M。丙醛能够与10-HCO-H（4）PteGlu竞争NADP（+）依赖性氧化，但对NADP+非依赖性水解酶反应没有影响。N-乙基马来酰亚胺抑制NADP（+）依赖性10-HCO-H（4）PteGlu氧化，但仅部分抑制（65%）水解酶活性。双硫仑是一种有效的胞质ALDH抑制剂，可抑制10-FTHFDH引起的NADP（+）依赖性丙醛氧化。我们建议，脱氢酶反应的10-FTHFDH有一个机制，通过硫代半缩醛和硫酯中间体，类似于醛脱氢酶所描述的。10-FTHFDH水解酶活性依赖于α-巯基乙醇，可能是测定系统的人为因素。10-FTHFDH的N-末端结构域显示与甘氨酰胺核糖核苷酸转化酶（EC www.example.com）相同，并含有推定的10-HCO-H（4）PteGlu结合位点，但不显示GAR-TF活性，10-FTHFDH对10-HCO-H（4）PteGlu的NADP（+）依赖性氧化被叶酸抗代谢物5，10-二脱氮四氢叶酸叶酸盐（一种已知的GAR-TF抑制剂）抑制。(C)出版社：Academic Press
10-Formyltetrahydrofolate dehydrogenase (10-FTHFDH: EC 1.5.1.6) catalyzes the NADP(+)-dependent oxidation of 10-formyltetrahydrofolate (10-HCO-H(4)PteGlu) to tetrahydrofolate (H(4)PteGlu) and CO2 and the NADP(+)-independent hydrolytic cleavage of 10-HCO-H(4)PteGlu to H(4)PteGlu and formate, 10-FTHFDH has a 485 amino acid domain at the C-terminus which is 46% identical to aldehyde dehydrogenase (ALDH: EC 1.2.1.3) and contains a conserved active site cysteine (Cys-707). 10-FTHFDH catalyzed NADP(+)-dependent oxidation of propanal and the hydrolysis of p-nitrophenyl acetate (pNPA) in a similar fashion to ALDH. Initial rate studies gave K-m values of 46 and 636 mu M, respectively, for NADP(+) and propanal, while pNPA had a K-m of 220 mu M. Propanal was able to compete with 10-HCO-H(4)PteGlu for NADP(+)-dependent oxidation but had no effect on the NADP+-independent hydrolase reaction. N-Ethylmaleimide inhibited NADP(+)-dependent 10-HCO-H(4)PteGlu oxidation but only partially inhibited (65%) hydrolase activity. Disulfiram, a potent inhibitor of cytosolic ALDH, inhibited NADP(+)-dependent propanal oxidation by 10-FTHFDH. We propose that the dehydrogenase reaction of 10-FTHFDH has a mechanism which proceeds through thiohemiacetal and thioester intermediates, similar to that described for aldehyde dehydrogenase. 10-FTHFDH hydrolase activity was dependent on a-mercaptoethanol and is probably an artifact of the assay system. The N-terminal domain of 10-FTHFDH shows identity to glycinamide ribonucleotide transformylase (EC 2.1.2.2) and contains a putative 10-HCO-H(4)PteGlu binding site but shows no GAR-TF activity, NADP(+)-dependent oxidation of 10-HCO-H(4)PteGlu by 10-FTHFDH was inhibited by the folate anti-metabolite, 5,10-dideazatetrahydrofolate folate, a known GAR-TF inhibitor. (C) 1995 Academic Press, Inc.