Hexaheme nitrite reductase from Desulfovibrio desulfuricans

Moessbauer and EPR spectroscopy were used to characterize the heme prosthetic groups of the nitrite reductase isolated from Desulfovibrio desulfuricans (ATCC 27774), which is a membrane-bound multiheme cytochrome capable of catalyzing the 6-electron reduction of nitrite to ammonia. At pH 7.6, the as...

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Published inThe Journal of biological chemistry Vol. 265:24
Main Authors Costa, C., Moura, J.J.G., Moura, I., Liu, M.Y., Peck, H.D. Jr, LeGall, J., Wang, Yaning, Huynh, B.H.
Format Journal Article
LanguageEnglish
Published United States 25.08.1990
Subjects
AMMONIA
BACTERIA
CARBOXYLIC ACIDS
CHEMICAL COMPOSITION
DESULFOVIBRIO
ELECTRON SPIN RESONANCE
ENZYMES
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
METABOLISM
MICROORGANISMS
NITRITES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT
RESONANCE
SULFATE-REDUCING BACTERIA 560300 > Chemicals Metabolism & Toxicology
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Summary:Moessbauer and EPR spectroscopy were used to characterize the heme prosthetic groups of the nitrite reductase isolated from Desulfovibrio desulfuricans (ATCC 27774), which is a membrane-bound multiheme cytochrome capable of catalyzing the 6-electron reduction of nitrite to ammonia. At pH 7.6, the as-isolated enzyme exhibited a complex EPR spectrum consisting of a low-spin ferric heme signal at g = 2.96, 2.28, and 1.50 plus several broad resonances indicative of spin-spin interactions among the heme groups. EPR redox titration studies revealed yet another low-spin ferric heme signal at g = 3.2 and 2.14 (the third g value was undetected) and the presence of a high-spin ferric heme. Moessbauer measurements demonstrated further that this enzyme contained six distinct heme groups: one high-spin (S = 5/2) and five low-spin (S = 1/2) ferric hemes. Characteristic hyperfine parameters for all six hemes were obtained through a detailed analysis of the Moessbauer spectra. D. desulfuricans nitrite reductase can be reduced by chemical reductants, such as dithionite or reduced methyl viologen, or by hydrogenase under hydrogen atmosphere. Addition of nitrite to the fully reduced enzyme reoxidized all five low-spin hemes to their ferric states. The high-spin heme, however, was found to complex NO, suggesting that the high-spin heme could be the substrate binding site and that NO could be an intermediate present in an enzyme-bound form.
Bibliography:None
ISSN:0021-9258
1083-351X