猪心二氢硫辛酰胺脱氢酶催化一氧化氮的NADH依赖性清除。

Dihydrolipoamide dehydrogenase from porcine heart catalyzes NADH-dependent scavenging of nitric oxide.

作者信息

Igamberdiev Abir U, Bykova Natalia V, Ens Werner, Hill Robert D

机构信息

Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.

出版信息

FEBS Lett. 2004 Jun 18;568(1-3):146-50. doi: 10.1016/j.febslet.2004.05.024.

DOI:10.1016/j.febslet.2004.05.024

PMID:15196936

Abstract

Dihydrolipoamide dehydrogenase (DLDH; EC 1.8.1.4) from porcine heart is capable of using nitric oxide (NO) as an electron acceptor, with NADH as the electron donor, forming nitrate in the reaction. NADPH was not effective as an electron donor. The reaction had a pH optimum near 6 and was not inhibited by cyanide or diphenyleneiodonium ions. The Km for NADH was 10 microM, while that for NO was 0.5 microM. The rate of NO conversion was comparable to the rate of lipoamide conversion (200 micromol min(-1) mg(-1) protein at pH 6). Cytochrome c or myoglobin were poor electron acceptors by themselves but, in the presence of methylene blue, DLDH had an activity of 5-7 micromol min(-1) mg(-1) protein with these substrates, indicating that DLDH can act also as a methemoglobin reductase. While the Km of DLDH for NO is relatively low, it is in the physiological range of NO levels encountered in the tissue. The enzyme may, therefore, have a significant role in modifying NO levels under specific cell conditions.

摘要

猪心二氢硫辛酰胺脱氢酶（DLDH；EC 1.8.1.4）能够以一氧化氮（NO）作为电子受体，以NADH作为电子供体，在反应中形成硝酸盐。NADPH作为电子供体无效。该反应的最适pH接近6，不受氰化物或二苯碘鎓离子的抑制。NADH的Km为10微摩尔，而NO的Km为0.5微摩尔。NO转化的速率与硫辛酰胺转化的速率相当（在pH 6时为200微摩尔·分钟⁻¹·毫克⁻¹蛋白质）。细胞色素c或肌红蛋白本身是较差的电子受体，但在亚甲蓝存在下，DLDH对这些底物具有5 - 7微摩尔·分钟⁻¹·毫克⁻¹蛋白质的活性，表明DLDH也可作为高铁血红蛋白还原酶。虽然DLDH对NO的Km相对较低，但处于组织中遇到的NO水平的生理范围内。因此，该酶可能在特定细胞条件下调节NO水平方面发挥重要作用。