Developing biomimetic complexes that model the active site of [NiFe] hydrogenase enzymes in order to catalyze the activation of H2 is a topic of major interest. A functional [NiFe] hydrogenase model complex has recently been described by Ogo et al. (Science, 2013, 339, 682-683). Here, we report a Mössbauer and computational investigation of this model complex. This study affords deeper understa...

The discovery of hydrogenase in Azotobacter cells (1) raises the question of its function in the metabolism of this organism. This enzyme is usually found in anaerobic or facultative anaerobic bacteria which liberate Hz from certain substrates. Azotobacter is a strict aerobe, and its metabolism consists primarily in the simple oxidation of substrate to carbon dioxide and water. Although not con...

The development of efficient biological systems for the direct photoproduction of H(2) gas from water faces several challenges, the more serious of which is the sensitivity of the H(2)-evolving enzymes (hydrogenases) to O(2), an obligatory by-product of photosynthesis. This high sensitivity is common to both FeFe and NiFe hydrogenases, and is caused by O(2) binding to their respective metalloca...

The roles of the product of the hoxZ gene immediately downstream of the hydrogenase gene (hoxKG) in Azotobacter vinelandii were investigated by constructing and characterizing a mutant with the center of the hoxZ gene deleted. The strain lacking the functional hoxZ gene product exhibited a low rate of H2 oxidation with O2 as the electron acceptor relative to that of the wild-type strain. Nevert...

A sensitive tritium exchange assay was applied to the Rhizobium system for measuring the expression of uptake hydrogenase in free-living cultures of Rhizobium japonicum. Hydrogenase was detected about 45 hours after inoculation of cultures maintained under microaerophilic conditions (about 0.1% O(2)). The tritium exchange assay was used to screen a variety of different strains of R. japonicum (...

The combination of enzymes with semiconductors enables the photoelectrochemical characterization of electron-transfer processes at highly active and well-defined catalytic sites on a light-harvesting electrode surface. Herein, we report the integration of a hydrogenase on a TiO2-coated p-Si photocathode for the photo-reduction of protons to H2. The immobilized hydrogenase exhibits activity on S...

Uptake hydrogenases in legume endosymbiotic bacteria recycle hydrogen produced during the nitrogen fixation process in legume nodules. Despite the described beneficial effect on plant productivity, the hydrogen oxidation capability is not widespread in the Rhizobiaceae family. Characterization of hydrogenase gene clusters in strains belonging to Rhizobium, Bradyrhizobium and Azorhizobium reveal...

Hydrogenases, which are ubiquitous in sulfate-reducing bacteria, were previously thought to be absent from Desulfuromonas acetoxidans. For the first time, a hydrogenase from the strict anaerobic sulfur-respiring bacterium D. acetoxidans, grown on ethanol-malate, was detected and enriched. To assay the role of the hydrogenase in the energetic metabolism of D. acetoxidans, we examined the reactiv...

Three cosmids previously shown to contain information necessary for the expression of uptake of hydrogenase in Rhodobacter capsulatus were found to be present in a cluster on the chromosome. Earlier genetic experiments suggested the presence of at least six genes essential for hydrogenase activity that are now shown to be in a region of approximately 18 kb that includes the structural genes for...

Hydrogenase [hydrogenase: (acceptor) oxidoreductase, EC 1.12. . -1 is present in many bacteria. It is one of the enzymes having potential use in the biophotolysis of water (Weaver et al.. 1980). When we began our research on hydrogenase in 1977, two types of enzymes were known: (i) enzymes containing 12 Fe atoms and an equivalent amount of acid-labile S atoms and (ii) enzymes containing only fo...