González Prieto J, Martín Sarmiento R, Burgos J
Arch Biochem Biophys. 1983 Jul 1;224(1):372-7. doi: 10.1016/0003-9861(83)90222-9.
Michaelis constants of L-glycol dehydrogenase from hen muscle (isozyme of pI 7.2) for the alpha-dicarbonyls tested (glyoxal, 2,3-pentanedione, methylglyoxal, and diacetyl) range from 35 microM for pentanedione to 0.41 mM for glyoxal. The enzyme shows a high affinity for NADPH, Km (2.2-3.1 microM), and Ks (1.2-1.9 microM) being so much lower than its tissue concentration that L-glycol dehydrogenase has to operate in vivo saturated with the coenzyme; this condition is very unfavorable to play a role in regulating the equilibrium oxidized/reduced forms of the pyridine nucleotides, as it has been proposed for some similar enzymes. Convergence of the double reciprocal plots and the pattern of inhibition by products and by acetone, a substrate analog, demonstrate that glyoxal reduction--and most likely that of diacetyl--proceeds via an ordered Bi-Bi mechanism in which NADPH is fixed before the addition of the carbonyl; the reduction of methylglyoxal and 2,3-pentanedione could follow the same model, but our experimental results are also consistent with that of Theorell-Chance.
鸡肌肉中L-甘油脱氢酶（pI 7.2的同工酶）对所测试的α-二羰基化合物（乙二醛、2,3-戊二酮、甲基乙二醛和双乙酰）的米氏常数范围从戊二酮的35微摩到乙二醛的0.41毫摩。该酶对NADPH具有高亲和力，其Km（2.2 - 3.1微摩）和Ks（1.2 - 1.9微摩）远低于其在组织中的浓度，以至于L-甘油脱氢酶在体内必须在辅酶饱和的状态下发挥作用；正如对一些类似酶所提出的那样，这种情况非常不利于在调节吡啶核苷酸的氧化/还原形式平衡中发挥作用。双倒数图的收敛以及产物和底物类似物丙酮的抑制模式表明，乙二醛的还原——很可能还有双乙酰的还原——通过有序的双底物双产物机制进行，其中NADPH在羰基添加之前就已结合；甲基乙二醛和2,3-戊二酮的还原可能遵循相同模式，但我们的实验结果也与Theorell-Chance机制一致。
