Chaiyen P, Brissette P, Ballou D P, Massey V
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606, USA.
Biochemistry. 1997 Mar 4;36(9):2612-21. doi: 10.1021/bi962325r.
The investigation by absorbance and fluorescence rapid reaction spectrophotometry of the binding of the substrate MHPC (2-methyl-3-hydroxypyridine-5-carboxylic acid) or the substrate analog 5HN (5-hydroxynicotinic acid) to the flavoprotein MHPCO (2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase) shows that the binding proceeds in two steps. An enzyme-substrate complex initially formed is followed by a ligand-induced isomerization. This binding process is required for efficient reduction of the enzyme-bound flavin, as evidenced by the fact that MHPCO-substrate complexes can be reduced by NADH much faster than the enzyme alone. Since redox potential values of MHPCO and MHPCO-substrate complexes are the same, steric factors, such as the relative orientation of MHPC to the enzyme-bound flavin, are important for efficient hydride transfer to occur.
通过吸光度和荧光快速反应分光光度法对底物MHPC（2-甲基-3-羟基吡啶-5-羧酸）或底物类似物5HN（5-羟基烟酸）与黄素蛋白MHPCO（2-甲基-3-羟基吡啶-5-羧酸加氧酶）结合的研究表明，结合过程分两步进行。最初形成的酶-底物复合物之后是配体诱导的异构化。这种结合过程对于酶结合黄素的有效还原是必需的，这一事实证明，MHPCO-底物复合物被NADH还原的速度比单独的酶快得多。由于MHPCO和MHPCO-底物复合物的氧化还原电位值相同，空间因素，如MHPC与酶结合黄素的相对取向，对于有效的氢化物转移发生很重要。
