Schauer N L, Ferry J G, Honek J F, Orme-Johnson W H, Walsh C
Biochemistry. 1986 Nov 4;25(22):7163-8. doi: 10.1021/bi00370a059.
Mechanistic studies have been undertaken on the coenzyme F420 dependent formate dehydrogenase from Methanobacterium formicicum. The enzyme was specific for the si face hydride transfer to C5 of F420 and joins three other F420-recognizing methanogen enzymes in this stereospecificity, consistent perhaps with a common type of binding site for this 8-hydroxy-5-deazariboflavin. While catalysis probably occurs by hydride transfer from formate to the enzyme to generate an EH2 species and then by hydride transfer back out to F420, the formate-derived hydrogen exchanged with solvent protons before transfer back out to F420. The kinetics of hydride transfer from formate revealed that this step is not rate determining, which suggests that the rate-determining step is an internal electron transfer. The deflavo formate dehydrogenase was amenable to reconstitution with flavin analogues. The enzyme was sensitive to alterations in FAD structure in the 6-, 7-, and 8-loci of the benzenoid moiety in the isoalloxazine ring.
已对来自甲酸甲烷杆菌的依赖辅酶F420的甲酸脱氢酶进行了机理研究。该酶对向F420的C5进行si面氢化物转移具有特异性，并在这种立体特异性方面与其他三种识别F420的产甲烷菌酶相同，这可能与这种8-羟基-5-脱氮核黄素的常见结合位点类型一致。虽然催化作用可能是通过氢化物从甲酸转移到酶上以生成EH2物种，然后再通过氢化物转移回F420，但来自甲酸的氢在转移回F420之前与溶剂质子发生了交换。从甲酸进行氢化物转移的动力学表明，这一步不是速率决定步骤，这表明速率决定步骤是内部电子转移。脱黄素甲酸脱氢酶适合用黄素类似物进行重组。该酶对异咯嗪环中苯并类部分的6-、7-和8-位点的FAD结构变化敏感。
