A purification procedure for the periplasmic hydrogenase from Desulfovibrio vulgaris ( Hildenborough , National Collection of Industrial Bacteria 8303) is reported. The purified hydrogenase has a specific activity of 4800 units per mg of protein. Plasma emission studies reveal that this highly active hydrogenase is free of nickel and contains 11 (+/- 1) nonheme iron atoms per molecule. A combin...

The mechanism of conversion of substrate hydrogen to H2 in microbial fermentations is still obscure. One of the enzymes presumably involved in the final phase of H2 formation is hydrogenase, which catalyzes the reaction H2 =2H+ + 2e (Stephenson and Stickland, 1931). The present investigation was stimulated by our interest in the presumed participation of hydrogenase in photochemical production ...

The IR carbonyl stretching frequencies of [Fe2(SRS)(CO)6] complexes correlate well with their first reduction potential; an [FeFe] hydrogenase model with a very mild reduction potential has been realized by using a strongly electron deficient carborane-dithiolate bridge.

A novel molecular triad [FeFe]-H(2)ase 1, and its model complexes 2 and 3 have been successfully constructed. The multistep PET and long-lived Fe(i)Fe(0) species were found to be responsible for the better performance of triad 1 than that of 2 with 3 for light-driven H(2) evolution.

This article summarizes recent advances in the field of algal hydrogen production. Two fundamental approaches are being developed. One involves the temporal separation of the usually incompatible reactions of O(2) and H(2) production in green algae, and the second involves the use of classical genetics to increase the O(2) tolerance of the reversible hydrogenase enzyme. The economic and environ...

Methanosarcina acetivorans C2A encodes three putative hydrogenases, including one cofactor F(420)-linked (frh) and two methanophenazine-linked (vht) enzymes. Comparison of the amino acid sequences of these putative hydrogenases to those of Methanosarcina barkeri and Methanosarcina mazei shows that each predicted subunit contains all the known residues essential for hydrogenase function. The DNA...

The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of ...

The inhibitors usually associated with the activity of the cytochrome oxidase system-cyanide and carbon monoxide-are also effective in reducing the oxidation of H(2) by intact cells of Azotobacter vinelandii. The hydrogenase system is more sensitive to CO than is the respiratory system. Oxidation of a carbon source and of hydrogen by Azotobacter cells is inhibited in a quantitatively different ...

The active site of [NiFe]-hydrogenase contains nickel and iron coordinated by cysteine residues, cyanide and carbon monoxide. Metal chaperone proteins HypA and HypB are required for the nickel insertion step of [NiFe]-hydrogenase maturation. How HypA and HypB work together to deliver nickel to the catalytic core remains elusive. Here we demonstrated that HypA and HypB from Archaeoglobus fulgidu...