title: On the structure of heme d1. An isobacteriochlorin derivative as the prosthetic group of dissimilatory nitrite reductase?
abstract: Timkovich and co-workers have recently proposed a chlorin macrocycle structure for the heme d1 prosthetic group isolated from cytochrome cd1 of Pseudomonas aeruginosa and Paracoccus denitrificans (Timkovich, R., Cork, M. S., and Taylor, P. V. (1984) J. Biol. Chem. 259, 1577-1585; 15089-15093). However, this chlorin structure deduced by them is not entirely consistent with the spectral data. An alternative structure is proposed here based on the available spectral evidence. It is suggested that heme d1 in vivo is not a chlorin, but a dioxo-isobacteriochlorin having two adjacent pyrrole rings saturated.
mesh_terms: D003574:Cytochrome c Group; D003580:Cytochromes / Q000032:analysis; D006418:Heme / Q000031:analogs & derivatives* / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D009247:NADH, NADPH Oxidoreductases / Q000032:analysis*; D009572:Nitrite Reductases / Q000032:analysis*; D010231:Paracoccus denitrificans / Q000201:enzymology; D011166:Porphyrins; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D003580:Cytochromes; D011166:Porphyrins; C006969:chlorin; D006418:Heme; C029400:heme d1; C019315:cytochrome cd1; D009247:NADH, NADPH Oxidoreductases; D009572:Nitrite Reductases