52 research outputs found
A glutathione-dependent formaldehyde-activating enzyme (Gfa) from Paracoccus denitrificans detected and purified via two- dimensional proton exchange NMR spectroscopy
The formation of S-hydroxymethylglutathione from formaldehyde and glutathione is a central reaction in the consumption of the cytotoxin formaldehyde in some methylotrophic bacteria as well as in many other organisms. We describe here the discovery of an enzyme from Paracoccus denitrificans that accelerates this spontaneous condensation reaction. The rates of S- hydroxymethylglutathione formation and cleavage were determined under equilibrium conditions via two-dimensional proton exchange NMR spectroscopy. The pseudo first order rate constants k(1)* were estimated from the temperature dependence of the reaction and the signal to noise ratio of the uncatalyzed reaction. At 303 K and pH 6.0 k(1)* was found to be 0.02 s(-1) for the spontaneous reaction. A 10-fold increase of the rate constant was observed upon addition of cell extract from P. denitrificans grown in the presence of methanol corresponding to a specific activity of 35 units mg(-1). Extracts of cells grown in the presence of succinate revealed a lower specific activity of 11 units mg(-1). The enzyme catalyzing the conversion of formaldehyde and glutathione was purified and named glutathione-dependent formaldehyde- activating enzyme (Gfa). The gene gfa is located directly upstream of the gene for glutathione-dependent formaldehyde dehydrogenase, which catalyzes the subsequent oxidation of S- hydroxymethylglutathione. Putative proteins with sequence identity to Gfa from P. denitrificans are present also in Rhodobacter sphaeroides, Sinorhizobium meliloti, and Mesorhizobium loti
Methyl-Coenzyme M Reductase from Methanogenic Archaea: Isotope Effects on the Formation and Anaerobic Oxidation of Methane
Formaldehyde activating enzyme (Fae) and hexulose-6-phosphate synthase (Hps) in Methanosarcina barkeri: a possible function in ribose-5-phosphate biosynthesis
Binding of Coenzyme B Induces a Major Conformational Change in the Active Site of Methyl-Coenzyme M Reductase
Methyl-Coenzyme M Reductase from Methanogenic Archaea: Isotope Effects on Label Exchange and Ethane Formation with the Homologous Substrate Ethyl-Coenzyme M
Temperature dependence of methyl-coenzyme M reductase activity and of the formation of the methyl-coenzyme M reductase red2 state induced by coenzyme B
Hydrogenases from methanogenic archaea, nickel, a novel cofactor, and H2 storage
Most methanogenic archaea reduce CO(2) with H(2) to CH(4). For the activation of H(2), they use different [NiFe]-hydrogenases, namely energy-converting [NiFe]-hydrogenases, heterodisulfide reductase-associated [NiFe]-hydrogenase or methanophenazine-reducing [NiFe]-hydrogenase, and F(420)-reducing [NiFe]-hydrogenase. The energy-converting [NiFe]-hydrogenases are phylogenetically related to complex I of the respiratory chain. Under conditions of nickel limitation, some methanogens synthesize a nickel-independent [Fe]-hydrogenase (instead of F(420)-reducing [NiFe]-hydrogenase) and by that reduce their nickel requirement. The [Fe]-hydrogenase harbors a unique iron-guanylylpyridinol cofactor (FeGP cofactor), in which a low-spin iron is ligated by two CO, one C(O)CH(2)-, one S-CH(2)-, and a sp(2)-hybridized pyridinol nitrogen. Ligation of the iron is thus similar to that of the low-spin iron in the binuclear active-site metal center of [NiFe]- and [FeFe]-hydrogenases. Putative genes for the synthesis of the FeGP cofactor have been identified. The formation of methane from 4 H(2) and CO(2) catalyzed by methanogenic archaea is being discussed as an efficient means to store H(2)
Two sub-states of the red2 state of methyl-coenzyme M reductase revealed by high-field EPR spectroscopy.
A glutathione-dependent formaldehyde-activating enzyme (Gfa) from Paracoccus denitrificans detected and purified via two- dimensional proton exchange NMR spectroscopy
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