Iron-sulfur proteins hydrogenases

This enzyme [EC 1.18.99.1], also known as hydrogenly-ase, catalyzes the reaction of H2 with two oxidized ferre-doxin to produce two H+ and two reduced ferredoxin. This enzyme is an iron-sulfur protein and requires nickel ions. It can use molecular hydrogen to reduce a variety of substances. See also Hydrogen Dehydrogenase Cytochrome C3 Hydrogenase... 

Based on the incomplete inhibition of iron-sulfur proteins by nitrite, and the observation that low-spin Fe—NO EPR signals were observed by C. sporogenes cultures that recovered from nitrite treatment, Payne et al. (1990a) concluded that the antimicrobial effect of nitrite or NO cannot be explained by direct inhibition of preformed pyruvate—ferredoxin oxidoreductase or hydrogenase. 

Hausmann A, Aguilar Netz DJ, Balk J, Pierik AJ, Muhlenhoff U, Lill R (2005) The eukaryotic P loop NTPase NBP35 An essential component of the cytosolic and nuclear iron-sulfur protein assembly machinery. Proc Natl Acad Sci USA 102 3266-3271 Henriquez FL, Richards , Roberts F, McLeod R, Roberts CW (2005) The unusual mitochondrial compartment of Cryptosporidium parvum. Trends Parasitol 21 68-74 Horner DS, Foster PG, Embley TM (2000) Iron hydrogenases and the evolution of anaerobic eukaryotes. Mol Biol Evol 17 1695-1709... 

The acidification of H2 may also be involved in hydrogenase action, where H2 is beheved to bind to an Fe(II) center. Isotope exchange between H2 and D2O is catalyzed by the enzyme see Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Iron-Sulfur Proteins). Similar isotope exchange can also occur in H2 complexes. Oxidative addition to give a classical dihydride is also a common reaction. [W(H2)(CO)3(PCy3)2] is in equilibrium with about 20% of the dihydride in solution. This can lead to subsequent hydrogenolysis of M-C bonds as in the case of a cyclometallated phenylpyridine complex of Ir(III). ... 

Simple iron-sulfur proteins, containing these basic structures are listed in Table 1. They are generally electron-transfer proteins mediating electron exchange between enzymatic systems, with the possible exception of hydrogenase, and aconitase, which might have catalytic activity of their own, as shall be discussed later. 

Fig. 7a. Epr spectra of reduced samples of the iron-sulfur proteins. Conditions of epr spectroscopy microwave frequency, 9.2 GHz microwave power, 0.9 mW modulation frequency, 100 KHz modulation amplitude, 10 G magnetic held sweep rate, 260 G/min time constant, 0.25 s sample temperature, I3°K. Abscissa, linear in field (g values corresponding to several field positions are given) ordinate, an arbitrary function of the first derivative of the microwave absorption, (a) Spinach ferredoxin (b) B. polymyxa Fd 11 (c) B. polymyxa fd I, all reduced with excess sodium dithionite (d) Clostridum acid-urici fd, in the presence of 0.06 atm of Hj, hydrogenase, and 0.1 M Tris HCI buffer, pH 8.0. The last sample is approximately half-reduced (from Stombaugh et al.. 1973).

Y. Guo, Initial studies on iron sulfur proteins and related model compounds via 57Fe and 6INi synchrotron radiation based perturbed angular correlations (SRPAC), in nuclear resonant scattering on nitrogenase, hydrogenase and model systems, Ph.D. thesis, 2009. 

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