Inoue Y, Rhee H, Watanabe K, Murata K, Kimura A
Research Institute for Food Science, Kyoto University, Japan.
Eur J Biochem. 1988 Jan 15;171(1-2):213-8. doi: 10.1111/j.1432-1033.1988.tb13778.x.
Two kinds of methylglyoxal reductases were purified to apparent homogeneity from Aspergillus niger and designated MGR I and MGR II. Both enzymes consisted of a single polypeptide chain with a relative molecular mass of 36,000 (MGR I) and 38,000 (MGR II). NADPH was specifically required for the activities of both enzymes and Km values for NADPH were 54 microM (MGR I) and 6.8 microM (MGR II). MGR I was specific to 2-oxoaldehydes [glyoxal, methylglyoxal (Km = 15.4 mM) and phenylglyoxal], whereas MGR II was active on both 2-oxoaldehydes [glyoxal (Km = 10 mM), methylglyoxal (Km = 1.43 mM), phenylglyoxal (Km = 4.35 mM) and 4,5-dioxovalerate] and some aldehydes (propionaldehyde and acetaldehyde). Optimal pH values for MGR I and MGR II activities were 9.0 and 6.5 respectively. Both enzymes were inactivated by a brief incubation with 2-oxoaldehydes (glyoxal, methylglyoxal and phenylglyoxal) in the absence of NADPH. MGR I activity was competitively inhibited by NADP+ and the Ki value for NADP+ was calculated to be 0.49 mM. On the other hand, the inhibition of MGR II activity by NADP+ was of mixed type, the Ki value for NADP+ being 45 microM. MGR I was different from MGR II in amino acid composition.
从黑曲霉中纯化出两种甲基乙二醛还原酶，达到表观均一，并分别命名为MGR I和MGR II。两种酶均由一条相对分子质量为36,000（MGR I）和38,000（MGR II）的单一多肽链组成。两种酶的活性都特别需要NADPH，NADPH的Km值分别为54μM（MGR I）和6.8μM（MGR II）。MGR I对2-氧代醛类[乙二醛、甲基乙二醛（Km = 15.4 mM）和苯乙二醛]具有特异性，而MGR II对2-氧代醛类[乙二醛（Km = 10 mM）、甲基乙二醛（Km = 1.43 mM）、苯乙二醛（Km = 4.35 mM）和4,5-二氧代戊酸]以及一些醛类（丙醛和乙醛）都有活性。MGR I和MGR II活性的最适pH值分别为9.0和6.5。在没有NADPH的情况下，两种酶与2-氧代醛类（乙二醛、甲基乙二醛和苯乙二醛）短暂孵育后均失活。MGR I的活性受到NADP +的竞争性抑制，NADP +的Ki值经计算为0.49 mM。另一方面，NADP +对MGR II活性的抑制属于混合型，NADP +的Ki值为45μM。MGR I和MGR II在氨基酸组成上有所不同。
