Hart G J, Dickinson F M
Biochem J. 1982 Jun 1;203(3):617-27. doi: 10.1042/bj2030617.
The kinetic properties of highly purified preparations of sheep liver cytoplasmic aldehyde dehydrogenase (preparations that had been shown to be free from contamination with the corresponding mitochondrial enzyme) were investigated with both propionaldehyde and butyraldehyde as substrates. At low aldehyde concentrations, double-reciprocal plots with aldehyde as the variable substrate are linear, and the mechanism appears to be ordered, with NAD+ as the first substrate to bind. Stopped-flow experiments following absorbance and fluorescence changes show bursts of NADH production in the pre-steady state, but the observed course of reaction depends on the pre-mixing conditions. Pre-mixing enzyme with NAD+ activates the enzyme in the pre-steady state and we suggest that the reaction mechanism may involve isomeric enzyme--NAD+ complexes. High concentrations of aldehyde in steady-state experiments produce significant activation (about 3-fold) at high concentrations of NAD+, but inhibition at low concentrations of NAD+. Such behaviour may be explained by postulating the participation of an abortive complex in product release. Stopped-flow measurements at high aldehyde concentrations indicate that the mechanism of reaction under these conditions is complex.
以丙醛和丁醛作为底物，对高度纯化的绵羊肝脏细胞质醛脱氢酶制剂（已证明不含相应线粒体酶污染的制剂）的动力学特性进行了研究。在低醛浓度下，以醛为可变底物的双倒数图呈线性，其机制似乎是有序的，NAD⁺是第一个结合的底物。跟踪吸光度和荧光变化的停流实验表明，在预稳态中有NADH生成的爆发，但观察到的反应进程取决于预混合条件。将酶与NAD⁺预混合会在预稳态中激活酶，我们认为反应机制可能涉及异构酶 - NAD⁺复合物。稳态实验中高浓度的醛在高浓度NAD⁺时产生显著激活（约3倍），但在低浓度NAD⁺时产生抑制。这种行为可以通过假定一种无效复合物参与产物释放来解释。在高醛浓度下的停流测量表明，在这些条件下的反应机制很复杂。
