Uotila L, Mannervik B
Biochem J. 1979 Mar 1;177(3):869-78. doi: 10.1042/bj1770869.
The steady-state kinetics of formaldehyde dehydrogenase from human liver have been explored. Non-linearities were obtained in v-versus-v[S] plots. It was necessary and sufficient to consider two reactants of the equilibrium mixture of formaldehyde, glutathione and their hemimercaptal adduct for a complete description of the kinetics. A random sequential reaction scheme is proposed in which adduct and beta-NAD+ are the substrates. In addition, glutathione can bind to an allosteric regulatory site and only the glutathione-containing enzyme is considered productive. Various alternative reaction models were examined but no simple alterative was superior to the model chosen. The discrimination was largely based on results of non-linear regression analysis. Several S-substituted glutathione derivatives were tested as activators or inhibitors of the enzyme, but all were without effect. Thio-NAD+, nicotinamide--hypoxanthine dinucleotide and 3-acetylpyridine-adenine dinucleotide could substitute for beta-NAD+ as the nucleotide substrate. alpha-NAD+ and ADP-ribose were competitive inhibitors with respect to beta-NAD+ and non-competitive with glutathione and the adduct. When used simultaneously, the inhibitors were linear competitive versus each other, indicating a single nucleotide-binding site or, if more than one, non-co-operative binding sites.
对人肝脏中的甲醛脱氢酶的稳态动力学进行了研究。在v对v[S]图中出现了非线性。要完整描述动力学，考虑甲醛、谷胱甘肽及其半硫醇加合物平衡混合物中的两种反应物是必要且充分的。提出了一种随机顺序反应方案，其中加合物和β-NAD⁺是底物。此外，谷胱甘肽可结合到变构调节位点，只有含谷胱甘肽的酶被认为具有活性。研究了各种替代反应模型，但没有一种简单的替代模型优于所选模型。这种区分主要基于非线性回归分析的结果。测试了几种S-取代的谷胱甘肽衍生物作为该酶的激活剂或抑制剂，但均无效果。硫代-NAD⁺、烟酰胺-次黄嘌呤二核苷酸和3-乙酰吡啶-腺嘌呤二核苷酸可替代β-NAD⁺作为核苷酸底物。α-NAD⁺和ADP-核糖对β-NAD⁺是竞争性抑制剂，对谷胱甘肽和加合物是非竞争性抑制剂。同时使用时，这些抑制剂相互呈线性竞争，表明存在单个核苷酸结合位点，或者如果有多个，则存在非协同结合位点。
