Properties of a Purified Halophilic Malic Dehydrogenase
Properties of a Purified Halophilic Malic Dehydrogenase
复制标题
纯化的嗜盐苹果酸脱氢酶的特性
DOI：
10.1128/jb.90.2.316-326.1965
复制
发表时间：
1965
影响因子：
3.2
通讯作者：
H. Halvorson
中科院分区：
文献类型：
--
作者：
P. K. Holmes;H. Halvorson
Holmes, P. K.（伊利诺伊大学厄巴纳分校）和 H. Orin Halvorson。纯化的嗜盐苹果酸脱氢酶的特性。 J.细菌。 90：316-326。 1965年——来自盐杆菌的苹果酸脱氢酶（MDH）需要高浓度的单价离子来保持稳定性和活性。对不同盐浓度下失活率的研究表明，需要大约 25% NaCl (w/v) 来稳定 MDH。根据失活过程中存在的盐浓度，2.5 至 5 m NaCl 或 KCl 中可能会发生 50% 至 100% 的再活化。 MDH 活性的最佳盐浓度是 pH 值的函数，范围为 1 至 3 m NaCl 或 KCl。盐浓度对 pH 值-活性曲线的影响主要发生在 pH 值低于 7.0 的情况下。用热或硫醇试剂灭活 MDH 表明，该酶在无盐诱导的状态下更不稳定。盐对 MDH 的激活归因于 MDH 解离速率的降低和烟酰胺腺嘌呤二核苷酸 (NADH2) 的还原。 NADH2 的存在可以在很大程度上防止在没有盐的情况下酶的失活。 MDH 的 S20.w 在低盐浓度下降低了三倍。假定该酶仅在高浓度盐存在的情况下才处于其天然紧凑构型。
Holmes, P. K. (University of Illinois, Urbana), and H. Orin Halvorson. Properties of a purified halophilic malic dehydrogenase. J. Bacteriol. 90:316–326. 1965.—The malic dehydrogenase (MDH) from Halobacterium salinarium required high concentrations of monovalent ions for stability and activity. Studies of inactivation rates at different salt concentrations suggested that approximately 25% NaCl (w/v) is required to stabilize MDH. From 50 to 100% reactivation, depending on the salt concentration present during inactivation, could occur in 2.5 to 5 m NaCl or KCl. The optimal salt concentration for activity of MDH was a function of the pH, and ranged from 1 to 3 m NaCl or KCl. The effect of salt concentration on the pH-activity curves occurred chiefly below pH 7.0. Inactivation of MDH with heat or thiol reagents showed that the enzyme was more labile in the state induced by absence of salt. The activation of MDH by salts was attributed to a decreased rate of dissociation of MDH and reduced nicotinamide adenine dinucleotide (NADH2). The inactivation of the enzyme in the absence of salt could be largely prevented by the presence of NADH2. The S20.w of MDH decreased threefold at low salt concentrations. The enzyme was assumed to be in its native compact configuration only in the presence of a high concentration of salt.