Oba K, Murakami S, Uritani I
J Biochem. 1977 May;81(5):1193-201.
Lactate dehydrogenase [L-lactate: NAD oxidoreductase, EC 1.1.1.27] was isolated from sweet potato root tissues. Two species of the enzyme (isozymes I and II) were separated by DE-52 cellulose column chromatography from healthy, cut, and black-rot diseased tissues. Isozymes I and II were purified from healthy and diseased tissues, respectively. Reduction of pyruvate by NADH with either isozyme I or II was inhibited by pyruvate at high concentrations, by NAD+ and by several mononucleotides. Isozyme I was inhibited by a lower concentration of adenine nucleotide than isozyme II, and Km for pyruvate was increased markedly at acidic pH in the case of isozyme I, but only slightly in the case of isozyme II. The molecular weights of both isozymes were determined to be 150,000 and they were found to be charge isomers by polyacrylamide gel electrophoresis. The enzyme activity increased in response to infection by black-rot fungus but decreased in response to cutting.
从甘薯根组织中分离出乳酸脱氢酶[L-乳酸：NAD氧化还原酶，EC 1.1.1.27]。通过DE-52纤维素柱色谱法从健康、切割和黑腐病组织中分离出两种该酶（同工酶I和II）。同工酶I和II分别从健康和患病组织中纯化得到。高浓度丙酮酸、NAD⁺和几种单核苷酸会抑制同工酶I或II催化的NADH对丙酮酸的还原反应。同工酶I比同工酶II更易受到较低浓度腺嘌呤核苷酸的抑制，并且在酸性pH条件下，同工酶I的丙酮酸Km值显著增加，而同工酶II仅略有增加。两种同工酶的分子量均测定为150,000，并且通过聚丙烯酰胺凝胶电泳发现它们是电荷异构体。该酶活性在受到黑腐病菌感染时增加，但在切割时降低。
