Reconstitution of [Fe]-hydrogenase using model complexes

• Published in: Nature chemistry 2015-12, Vol.7 (12), p.995-1002
• Main Authors: Shima, Seigo, Chen, Dafa, Xu, Tao, Wodrich, Matthew D., Fujishiro, Takashi, Schultz, Katherine M., Kahnt, Jörg, Ataka, Kenichi, Hu, Xile
• Format: Article
• Language: English
• Subjects: 119/118; 639/638/263/49/1141; 639/638/45/173; 639/638/45/607; 639/638/77/603; Analytical Chemistry; Biochemistry; Carbon dioxide; Catalytic Domain; Chemistry; Chemistry/Food Science; Coenzymes - chemistry; Coenzymes - metabolism; Hydrogen - chemistry; Hydrogen - metabolism; Hydrogenase - chemistry; Hydrogenase - metabolism; Hydrogenation; Inorganic Chemistry; Iron-Sulfur Proteins - chemistry; Iron-Sulfur Proteins - metabolism; Methanogenesis; Models, Molecular; Molecular Structure; Organic Chemistry; Physical Chemistry; Pterins - chemistry; Pterins - metabolism; Pyridines - chemistry; Pyridines - metabolism; Thermodynamics
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.2382

[Fe]-Hydrogenase catalyses the reversible hydrogenation of a methenyltetrahydromethanopterin substrate, which is an intermediate step during the methanogenesis from CO 2 and H 2 . The active site contains an iron-guanylylpyridinol cofactor, in which Fe 2+ is coordinated by two CO ligands, as well as an acyl carbon atom and a pyridinyl nitrogen atom from a 3,4,5,6-substituted 2-pyridinol ligand. However, the mechanism of H 2 activation by [Fe]-hydrogenase is unclear. Here we report the reconstitution of [Fe]-hydrogenase from an apoenzyme using two FeGP cofactor mimics to create semisynthetic enzymes. The small-molecule mimics reproduce the ligand environment of the active site, but are inactive towards H 2 binding and activation on their own. We show that reconstituting the enzyme using a mimic that contains a 2-hydroxypyridine group restores activity, whereas an analogous enzyme with a 2-methoxypyridine complex was essentially inactive. These findings, together with density functional theory computations, support a mechanism in which the 2-hydroxy group is deprotonated before it serves as an internal base for heterolytic H 2 cleavage. [Fe]-hydrogenase has an iron-guanylylpyridinol cofactor and catalyses the reversible hydrogenation of a methenyl-tetrahydromethanopterin. Now, [Fe]-hydrogenase has been reconstituted using synthetic cofactor mimics. The enzyme containing a mimic with a 2-hydroxy-pyridine group was active, whereas one containing a 2-methoxy-pyridine group was inactive. This result, together with DFT computations, supports a catalytic mechanism involving the deprotonated pyridinol hydroxy group as a proton acceptor.