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Production of Clean Energy from Cyanobacterial Biochemical Products
Published in Stephen A. Roosa, International Solutions to Sustainable Energy, Policies and Applications, 2020
The biological role of bidirectional or reversible hydrogenase is thought to control ion levels in the organism. Reversible hydrogenase is associated with the cytoplasmic membrane and likely functions as an electron acceptor from both NADH and H2 [12]. The reversible hydrogenase is a multimeric enzyme consisting of either four or five different subunits depending on the species [12,34]. On a molecular scale, it is a NiFe-hydrogenase of the NAD(P)+ reducing type which consists of a hydrogenase dimmer coded by hoxYH gene. Maturation of reversible hydrogenases requires the action of several auxiliary proteins collectively termed as hyp (products of genes: hypF, hypC, hypD, hypE, hypA, and hypB) [44]. Unlike uptake hydrogenase, reversible hydrogenases are helpful in hydrogen production. Most cyano-bacterial species preferentially absorb red light near 680 nm [31], the light required for hydrogen production.
Hydrogen Photoproduction by Oxygenic Photosynthetic Microorganisms
Published in Farshad Darvishi Harzevili, Serge Hiligsmann, Microbial Fuels, 2017
Fabrice Franck, Bart Ghysels, Damien Godaux
These enzymes are common in prokaryotes with numerous representatives in bacteria and archaea. [NiFe]-Hydrogenase forms globular heteromultimers (Volbeda et al., 1995) where the bimetallic NiFe active site is coordinated by four cysteines and three nonprotein ligands, one carbon monoxide (CO) molecule, and two cyanide ions (CN), bound to the Fe atom (Happe et al., 1997; Pierik et al., 1999). The NiFe cluster is located in the large subunit and deeply buried in the protein. The small subunit contains several Fe-S clusters that conduct electrons from the active site to the physiological electron acceptor or donor. The [4Fe-4S] cluster proximal to the active site is regarded as essential for activity (Albracht, 1994). In additional to structural genes, there are accessory genes for maturation and the insertion of Ni, Fe, CO, and CN at the active site of the heterodimer. The maturation of hydrogenases follows a complex pathway, which involves at least seven auxiliary proteins (HypA-F and an endopeptidase). The corresponding genes are clustered in a majority of host organisms, and transcriptional control is regulated by several factors, including hydrogen, oxygen, carbon monoxide, and redox state of the cell.
Progress in microbiology for fermentative hydrogen production from organic wastes
Published in Critical Reviews in Environmental Science and Technology, 2019
[NiFe]-hydrogenases are the most-studied classes of hydrogenases. All [NiFe]-hydrogenases have a common heterodimeric core that resembles the first structure of the enzyme from Desulfivibrio gigas published by Zhang et al. (Schleucher et al., 1999). The structure of [NiFe]-hydrogenases comprises a large (L) subunit and a small subunit. The small subunit is composed of two structural domains called IS and IIS. Three FeS clusters that are responsible for transferring electrons to and from the active site. IS has a flavodoxin-like topology, and it binds [Fe4S4]; IIS lacks extensive secondary structure, and it binds the rest two FeS clusters: mesial [Fe3S4] and distal [Fe4S4]. All the remaining protein ligands to the FeS clusters are cysteine thiolates. The active site is located in the hydrogenase L subunit, similar to [Fe]-hydrogenase, it is buried in the protein, which shows two strong peaks of Ni and Fe in the initial 2.85 A ° resolution electron density map. Figure 4 shows the nickel–iron active site of D. gigas [NiFe]-hydrogenase, it contains two cis sites available for substrate binding: a bridging site between Fe and Ni, called E2, and a Ni-terminal one called E1. During the reaction, electrons and protons need to transfer between the catalytic center and the molecular surface. Thus, it requires the molecular hydrogen access the active site or escape from it to achieve the consumption and generation of hydrogen.