[NiFe] and [FeFe] Hydrogenases Studied by Advanced Magnetic Resonance Techniques

Abstract

Physical chemistry Z 0225 [NiFe] and [FeFe] Hydrogenases Studied by Advanced Magnetic Resonance Techniques -[342 refs.]. -(LUBITZ*, W.; REIJERSE, E.; VAN GASTEL, M.; Chem. Rev. (Washington, D. C.) 107 (2007) 10, 4331-4365; MPI Bioanorg. Chem., D-45470 Muelheim/R., Germany; Eng.) -Schramke 50-258

Hydrogen production by nitrogenase as a potential crop rotation benefit

“…Some hydrogenases are oxygen tolerant, but most are not (Lubitz et al 2007) and though not as sensitive as nitrogenase (Van Soom et al 1993), hydrogenases can still be inactivated by O 2 or even irreversibly damaged if exposed to high enough pO 2 (Lubitz et al 2007); the nature of this O 2 inhibition is not yet known, but it has been postulated that it may be due to a reaction occurring with O 2 somewhere near the active site of the enzyme (Lubitz et al 2007). Inhibition of hydrogenase can also occur with copper or mercury salts, but the mechanism for this inhibition is also unknown (Lubitz et al 2007).…”

“…A [4Fe-4S] cluster located proximal to the active site is essential for H 2 activation (Vignais and Colbeau 2004). The binding site of H 2 has not been determined, but it is hoped that magnetic resonance imaging (MRI) will be able to provide the answer (Lubitz et al 2007). In rhizobial species, the O 2 -dependent, Ni 2?…”

“…The NiFe site is buried deep within the centre of the enzyme, coordinated to the rest of the protein by four cysteines (Vignais and Colbeau 2004), while the Fe atoms of the Fe-S clusters are ligated by small inorganic ligands such as CO and CN - (Lubitz et al 2007). The small subunit contains up to three Fe-S clusters, which conduct electrons between the H 2 -activating centre and the electron acceptor or donor of the hydrogenase (Vignais and Colbeau 2004).…”

Microbial Sensor Systems for Dihydrogen, Nitric Oxide, and Carbon Monoxide

“…These signals are characteristic for the oxidized, catalytically inactive resting states of the standard [NiFe]-hydrogenase. In this case conversion of the enzyme to the active state, which implies the reductive removal of oxygen from the Ni-Fe site, may take hours (Ni-A) or minutes (Ni-B) [18]. The fact that the RH instantaneously reacts with H 2 [17] is compatible with its function of a sensing protein that needs to be on alert the moment H 2 occurs in the environment.…”

“…(i) Compared to standard [NiFe]-hydrogenases that display a specific activity of approximately 30-80 U/mg protein, the activity of RH proteins is approximately two orders of magnitude lower [17]. (ii) The electron paramagnetic resonance (EPR) spectrum of the RH lacks two EPR signals (Ni-A, Ni-B) from the nickel-based unpaired spin [18]. These signals are characteristic for the oxidized, catalytically inactive resting states of the standard [NiFe]-hydrogenase.…”