Place A R, Powers D A
J Biol Chem. 1984 Jan 25;259(2):1299-308.
In order to evaluate whether structural differences exist between allelic variants of a B-type lactate dehydrogenase (LDH; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) in the minnow Fundulus heteroclitus, the allozymes (LDH-Ba4, LDH-Ba/Bb, and LDH-Bb4) were purified to homogeneity by affinity chromatography. Each variant was characterized as to holoenzyme and subunit molecular mass, isoelectric point (pI), thermal and urea stability, and susceptibility to proteolysis. Differences in electrophoretic mobilities were due to a lower pI for LDH-Ba4 (pI = 6.6) than for LDH-Bb4 (pI = 7.2). Stability to inactivation by heat, urea, and proteolysis was in each case: LDH-Bb4 greater than LDH-Ba/Bb greater than LDH-Ba4. Inactivation by trypsin may involve the arginine-rich catalytic loop of lactate dehydrogenase (50). The results suggest that the allozymes differ in their conformational flexibility.
为了评估米诺鱼（Fundulus heteroclitus）中B型乳酸脱氢酶（LDH；L-乳酸：NAD⁺氧化还原酶，EC 1.1.1.27）等位基因变体之间是否存在结构差异，通过亲和色谱法将同工酶（LDH-Ba4、LDH-Ba/Bb和LDH-Bb4）纯化至同质。对每个变体的全酶和亚基分子量、等电点（pI）、热稳定性和尿素稳定性以及对蛋白水解的敏感性进行了表征。电泳迁移率的差异是由于LDH-Ba4（pI = 6.6）的pI低于LDH-Bb4（pI = 7.2）。在每种情况下，热、尿素和蛋白水解失活的稳定性为：LDH-Bb4大于LDH-Ba/Bb大于LDH-Ba4。胰蛋白酶导致的失活可能涉及乳酸脱氢酶富含精氨酸的催化环（50）。结果表明，这些同工酶在构象灵活性方面存在差异。
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