Ferric-dioxoisobacteriochlorin

More prevalent is cytochrome cd2 nitrite reductase.340 343 346 The water-soluble periplasmic enzyme is a homodimer of 60-kDa subunits, each containing a c-type heme in a small N-terminal domain and heme dv a ferric dioxoisobacteriochlorin (Fig. 16-6). The... 

These enzymes are homodimeric periplasmic proteins (encoded by nirB) that contain two different heme groups per monomer. One is a c-type heme bound via a Cys-X-X-Cys-His motif and has a role in electron transfer the other, a noncovalently linked d heme, is an unusual ferric-dioxoisobacteriochlorin, restricted to this class of enzyme and forms the active site. The biosynthetic pathway of heme di is unique among the tetrapyrroles in having 0x0, methyl, and acrylate side chains, involving some seven nir genes. The Em values of heme d model complexes are 200mV lower than iron porphyrins. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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