{"title":"Structural basis for altered activity of M‐ and H‐isozyme forms of human lactate dehydrogenase","authors":"J. Read, V. J. Winter, C. Eszes, R. Sessions, R. L. Brady","doi":"10.1002/1097-0134(20010501)43:2<175::AID-PROT1029>3.0.CO;2-#","DOIUrl":null,"url":null,"abstract":"Lactate dehydrogenase (LDH) interconverts pyruvate and lactate with concomitant interconversion of NADH and NAD+. Although crystal structures of a variety of LDH have previously been described, a notable absence has been any of the three known human forms of this glycolytic enzyme. We have now determined the crystal structures of two isoforms of human LDH—the M form, predominantly found in muscle; and the H form, found mainly in cardiac muscle. Both structures have been crystallized as ternary complexes in the presence of the NADH cofactor and oxamate, a substrate‐like inhibitor. Although each of these isoforms has different kinetic properties, the domain structure, subunit association, and active‐site regions are indistinguishable between the two structures. The pKa that governs the KM for pyruvate for the two isozymes is found to differ by about 0.94 pH units, consistent with variation in pKa of the active‐site histidine. The close similarity of these crystal structures suggests the distinctive activity of these enzyme isoforms is likely to result directly from variation of charged surface residues peripheral to the active site, a hypothesis supported by electrostatic calculations based on each structure. Proteins 2001;43:175–185. © 2001 Wiley‐Liss, Inc.","PeriodicalId":20789,"journal":{"name":"Proteins: Structure","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2001-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"197","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Proteins: Structure","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1002/1097-0134(20010501)43:2<175::AID-PROT1029>3.0.CO;2-#","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 197
人乳酸脱氢酶M -和H -同工酶活性改变的结构基础
乳酸脱氢酶(LDH)将丙酮酸和乳酸相互转化,同时NADH和NAD+相互转化。虽然以前已经描述了各种乳酸脱氢酶的晶体结构,但值得注意的是,这种糖酵解酶的三种已知人类形式中的任何一种都没有。我们现在已经确定了人类ldh的两种异构体的晶体结构——主要存在于肌肉中的M型;H型主要存在于心肌中。这两种结构都在NADH辅助因子和草酸盐(一种底物样抑制剂)存在下结晶为三元配合物。尽管这些同工异构体具有不同的动力学性质,但两种结构之间的结构域、亚基关联和活性位点区域是无法区分的。研究发现,控制两种同工酶的丙酮酸KM的pKa相差约0.94 pH单位,与活性位点组氨酸的pKa变化一致。这些晶体结构的密切相似性表明,这些酶同种异构体的独特活性可能直接源于活性位点周围带电表面残基的变化,这一假设得到了基于每种结构的静电计算的支持。蛋白质2001;43:175 - 185。©2001 Wiley‐Liss, Inc。
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