A preliminary account of the properties of recombinant human glyoxylate reductase (GRHPR), LDHA and LDHB with glyoxylate, and their potential roles in its metabolism
A preliminary account of the properties of recombinant human glyoxylate reductase (GRHPR), LDHA and LDHB with glyoxylate, and their potential roles in its metabolism
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DOI：
10.1016/j.bbapap.2005.08.004
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发表时间：
2005-12-01
影响因子：
3.2
通讯作者：
Rumsby, G
中科院分区：
文献类型：
--
作者：
Mdluli, K;Booth, MPS;Rumsby, G
人乳酸脱氢酶（LDH）被认为有助于乙醛酸氧化为草酸，从而导致内源性草酸过量产生疾病的发病机制。乙醛酸还原酶 (GRHPR) 具有潜在的保护作用，可将乙醛酸代谢为反应性较低的乙醇酸。本文比较了重组人 LDHA、LDHB 和 GR 的动力学参数及其对乙醛酸和相关底物的亲和力。测定纯化的重组人 LDHA、LDHB 和 GRHPR 的 K(m) 值和特异性常数 (K(cat)/K(m))，以减少乙醛酸和羟基丙酮酸。乙醛酸的 Km 值对于 LDHA 为 29.3 mM，对于 LDHB 为 9.9 mM，对于 GRHPR 为 1.0 mM。对于乙醛酸的氧化，以 NAD(+) 作为辅助因子，LDHA 和 LDHB 的 K(m) 值分别为 0.18 mM 和 0.26 mM。总体而言，在相同的反应条件下，特异性常数表明这些底物的还原和氧化反应之间存在良好的平衡，表明控制很可能由各自细胞内辅因子的环境浓度决定。 LDHA 和 LDHB 都不利用乙醇酸作为底物，NADPH 是一种较差的辅助因子，其相对活性低于 NADH 的 3%。 GRHPR 对 NADPH 的亲和力高于 NADH（K(M) 0.011 mM vs. 2.42 mM）。讨论了 LDH 异构体和 GRHPR 在草酸盐合成中的潜在作用。 (c) 2005 Elsevier B.V 保留所有权利。
Human lactate dehydrogenase (LDH) is thought to contribute to the oxidation of glyoxylate to oxalate and thus to the pathogenesis of disorders of endogenous oxalate overproduction. Glyoxylate reductase (GRHPR) has a potentially protective role metabolising glyoxylate to the less reactive glycolate. In this paper, the kinetic parameters of recombinant human LDHA, LDHB and GR have been compared with respect to their affinity for glyoxylate and related substrates. The K(m) values and specificity constants (K(cat)/K(m)) of purified recombinant human LDHA, LDHB and GRHPR were determined for the reduction of glyoxylate and hydroxypyruvate. Km values with glyoxylate were 29.3 mM for LDHA, 9.9 mM for LDHB and 1.0 mM for GRHPR. For the oxidation of glyoxylate, K(m) values were 0.18 mM and 0.26 mM for LDHA and LDHB respectively with NAD(+) as cofactor. Overall, under the same reaction conditions, the specificity constants suggest there is a fine balance between the reduction and oxidation reactions of these substrates, suggesting that control is most likely dictated by the ambient concentrations of the respective intracellular cofactors. Neither LDHA nor LDHB utilised glycolate as substrate and NADPH was a poor cofactor with a relative activity less than 3% that of NADH. GRHPR had a higher affinity for NADPH than NADH (K(M) 0.011 mM vs. 2.42 mM). The potential roles of LDH isoforms and GRHPR in oxalate synthesis are discussed. (c) 2005 Elsevier B.V All rights reserved.