Izumi Y, Yoshida T, Kanzaki H, Toki S, Miyazaki S S, Yamada H
Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto University, Japan.
Eur J Biochem. 1990 Jun 20;190(2):279-84. doi: 10.1111/j.1432-1033.1990.tb15573.x.
Hydroxypyruvate reductase of a serine-producing methylotroph, Hyphomicrobium methylovorum GM2, was purified to complete homogeneity, crystallized and characterized, the first time for an enzyme from a methylotroph. The enzyme was found to be a dimer composed of identical subunits (38 kDa), the molecular mass of the enzyme being about 70 kDa. The enzyme was stable against heating at 25 degrees C for 10 min at pH values between 5 and 9. Optimal activity was observed at pH 6.8 and around 45 degrees C. The enzyme catalyzed the reduction of hydroxypyruvate with the oxidation of only NADH. Other than hydroxypyruvate, only glyoxylate served as a substrate. The Km values were found to be 0.175 mM for hydroxypyruvate and 10.8 mM for glyoxylate. Taking advantage of the high substrate specificity of this enzyme, a means of enzymatic determination of hydroxypyruvate was established.
产丝甲基营养菌——卵形生丝微菌GM2的羟基丙酮酸还原酶被纯化至完全同质，进行了结晶和表征，这是首次对来自甲基营养菌的一种酶进行此类操作。该酶被发现是由相同亚基（38 kDa）组成的二聚体，酶的分子量约为70 kDa。在pH值5至9之间，该酶在25℃加热10分钟仍保持稳定。在pH 6.8和45℃左右观察到最佳活性。该酶催化羟基丙酮酸的还原反应，同时仅氧化NADH。除了羟基丙酮酸外，只有乙醛酸可作为底物。发现羟基丙酮酸的Km值为0.175 mM，乙醛酸的Km值为10.8 mM。利用该酶的高底物特异性，建立了一种酶法测定羟基丙酮酸的方法。
