title: Biosynthesis and functional role of haem O and haem A.
abstract: Haem O and/or haem A are specifically synthesized for the haem-copper respiratory oxidases. A 17-carbon hydroxyethylfarnesyl chain at the pyrrole ring A of the haems seems essential for catalytic functions at the oxygen-reduction site. The discovery of haem O in the cytochrome bo complex from Escherichia coli was a breakthrough in the studies on haem A biosynthesis. Molecular biological and biochemical studies in the past three years demonstrated that the cyoE/ctaB/COX10 genes are indispensable for functional expression of the terminal oxidases and encode a novel enzyme haem O synthase (protohaem IX farnesyltransferase). It has recently been suggested that the ctaA gene adjacent to the ctaB-ctaCDEF gene cluster in Bacillus subtilis encodes haem A synthase (haem O monooxygenase). In this article, we review current knowledge of the genes for haem O and haem A biosyntheses, the location and regulation of haem O synthase, the possible enzymatic mechanism of farnesyl transfer to haem B and the possible roles of the farnesylated haems.
authors.affiliation: Department of Plant Sciences, Graduate School of Science, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Mogi
authors.forename: K
authors.initials: K
authors.lastname: Saiki
authors.forename: Y
authors.initials: Y
authors.lastname: Anraku
mesh_terms: D019883:Alkyl and Aryl Transferases; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D006418:Heme / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D005810:Multigene Family; D014166:Transferases / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; C069808:heme O; C027728:heme a; D006418:Heme; C017168:cytochrome bo, E coli; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C078356:CyoE protein, Bacteria; C489727:CyoE protein, E coli