Izaguirre G, Kikonyogo A, Pietruszko R
Center of Alcohol Studies, Rutgers University, Piscataway, NJ 08854-8001, USA.
Comp Biochem Physiol B Biochem Mol Biol. 1998 Apr;119(4):747-54. doi: 10.1016/s0305-0491(98)00051-0.
Methylglyoxal was demonstrated to be a substrate for the isozymes E1, E2 and E3 of human aldehyde dehydrogenase. Pyruvate was the product from the oxidation of methylglyoxal by the three isozymes. At pH 7.4 and 25 degrees C, the major and minor components of the E3 isozyme catalyzed the reaction with Vmax of 1.1 and 0.8 mumol NADH min-1 mg-1 protein, respectively, compared to 0.067 and 0.060 mumol NADH min-1 mg-1 protein for the E1 and E2 isozymes, respectively. The E2 isozyme had a K(m) for methylglyoxal of 8.6 microM, the lowest compared to 46 microM for E1 and 586 and 552 microM for the major and minor components of the E3 isozyme, respectively. Both components of the E3 isozyme showed substrate inhibition by methylglyoxal, with Ki values of 2.0 mM for the major component and 12 mM for the minor component at pH 9.0. Substrate inhibition by methylglyoxal was not observed with the E1 and E2 isozymes. Methylglyoxal strongly inhibited the glycolaldehyde activity of the E1 and E2 isozymes. Mixed-type models of inhibition were employed as an approach to calculate the inhibition constants, 44 and 10.6 microM for E1 and E2 isozymes, respectively.
已证明甲基乙二醛是人类醛脱氢酶同工酶E1、E2和E3的底物。丙酮酸是这三种同工酶氧化甲基乙二醛的产物。在pH 7.4和25℃条件下，E3同工酶的主要和次要组分催化该反应的Vmax分别为1.1和0.8 μmol NADH min⁻¹ mg⁻¹蛋白质，相比之下，E1和E2同工酶的Vmax分别为0.067和0.060 μmol NADH min⁻¹ mg⁻¹蛋白质。E2同工酶对甲基乙二醛的K(m)为8.6 μM，是三种同工酶中最低的，相比之下，E1为46 μM，E3同工酶的主要和次要组分分别为586和552 μM。在pH 9.0时，E3同工酶的两个组分均表现出甲基乙二醛对底物的抑制作用，主要组分的Ki值为2.0 mM，次要组分的Ki值为12 mM。未观察到E1和E2同工酶存在甲基乙二醛对底物的抑制作用。甲基乙二醛强烈抑制E1和E2同工酶的乙醇醛活性。采用混合型抑制模型来计算抑制常数，E1和E2同工酶的抑制常数分别为44和10.6 μM。
