Isolation and characterization of a thermostable F420:NADPH oxidoreductase from Thermobifida fusca
作者:Hemant Kumar、Quoc-Thai Nguyen、Claudia Binda、Andrea Mattevi、Marco W. Fraaije
DOI:10.1074/jbc.m117.787754
日期:2017.6
F420H2-dependent enzymes reduce a wide range of substrates that are otherwise recalcitrant to enzyme-catalyzed reduction, and their potential for applications in biocatalysis has attracted increasing attention. Thermobifida fusca is a moderately thermophilic bacterium and holds high biocatalytic potential as a source for several highly thermostable enzymes. We report here on the isolation and characterization of a thermostable F-420: NADPH oxidoreductase (Tfu-FNO) from T. fusca, the first F-420-dependent enzyme described from this bacterium. Tfu-FNO was heterologously expressed in Escherichia coli, yielding up to 200 mg of recombinant enzyme per liter of culture. We found that Tfu-FNO is highly thermostable, reaching its highest activity at 65 degrees C and that Tfu-FNO is likely to act in vivo as an F-420 reductase at the expense of NADPH, similar to its counterpart in Streptomyces griseus. We obtained the crystal structure of FNO in complex with NADP(+) at 1.8 angstrom resolution, providing the first bacterial FNO structure. The overall architecture and NADP(+)-binding site of Tfu-FNO were highly similar to those of the Archaeoglobus fulgidus FNO (Af- FNO). The active site is located in a hydrophobic pocket between an N-terminal dinucleotide binding domain and a smaller C-terminal domain. Residues interacting with the 2' -phosphate of NADP (+) were probed by targeted mutagenesis, indicating that Thr-28, Ser-50, Arg-51, and Arg-55 are important for discriminating between NADP(+) and NAD(+). Interestingly, a T28A mutant increased the kinetic efficiency > 3-fold as compared with the wild-type enzyme when NADH is the substrate. The biochemical and structural data presented here provide crucial insights into the molecular recognition of the two cofactors, F-420 and NAD(P) H by FNO.
by superimposing the polypeptide after fixing hydride‐transferring atoms of the flavins on each other, and by the subsequent transfer of the methyl‐tetrahydropterin from MTHFR to jMer. Mutational analysis of four functional amino acids, which are similarly positioned in the three reductase structures, indicated despite the insignificant sequence identity, a common catalytic mechanism with a 5‐iminium
亚甲基四氢蝶呤还原酶催化亚甲基还原为与还原蝶呤结合的甲基,即 C 1各种单碳载体(C 1 )新陈代谢。 F第420章依赖的亚甲基四氢甲蝶呤(亚甲基-H 4 MPT)还原酶(Mer)和不依赖黄素的亚甲基四氢叶酸(亚甲基-H) 4 F) 还原酶 (Mfr) 使用三元复合机制直接从 F 转移氢化物第420章H 2和NAD(P)H连接到各自的亚甲基,而FAD依赖的亚甲基-H 4 F还原酶(MTHFR)以FAD为辅基,通过乒乓机制催化亚甲基-H的还原4 F. MTHFR的三元配合物结构及其衍生的催化机制是可用的,但Mfr或Mer的三元配合物结构尚未报道。在这里,梅尔来自詹氏甲烷球菌(jMer) 是异源产生的,并且具有和不具有 F 的酶的晶体结构第420章被确定。 jMer的三元复合物是在jMer-F的基础上建模的第420章通过将黄素的氢化物转移原子固定后的多肽相互叠加,以及随后将甲基四氢蝶呤从MTH