title: Isolation and characterization of 14 additional genes specifying the anaerobic biosynthesis of cobalamin (vitamin B12) in Propionibacterium freudenreichii (P. shermanii).
abstract: A search for genes encoding enzymes involved in cobalamin (vitamin B12) production in the commercially important organism Propionibacterium freudenreichii (P. shermanii) has resulted in the isolation of an additional 14 genes encoding enzymes responsible for 17 steps of the anaerobic B12 pathway in this organism. All of the genes believed to be necessary for the biosynthesis of adenosylcobinamide from uroporphyrinogen III have now been isolated except two (cbiA and an as yet unidentified gene encoding cobalt reductase). Most of the genes are contained in two divergent operons, one of which, in turn, is closely linked to the operon encoding the B12-dependent enzyme methylmalonyl-CoA mutase. The close linkage of the three genes encoding the subunits of transcarboxylase to the hemYHBXRL gene cluster is reported. The functions of the P. freudenreichii B12 pathway genes are discussed, and a mechanism for the regulation of cobalamin and propionic acid production by oxygen in this organism is proposed.
authors.affiliation: Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Roessner
authors.affiliation: Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1.
authors.forename: Ke-Xue
authors.initials: KX
authors.lastname: Huang
authors.affiliation: School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK2.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Warren
authors.affiliation: School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK2.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Raux
authors.affiliation: Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1.
authors.forename: A Ian
authors.initials: AI
authors.lastname: Scott
mesh_terms: D000693:Anaerobiosis; D001483:Base Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D003035:Cobalt / Q000378:metabolism; D016384:Consensus Sequence; D005798:Genes, Bacterial / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D011424:Propionibacterium / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D014577:Uroporphyrinogens / Q000378:metabolism; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D014577:Uroporphyrinogens; C010895:cobyrinic acid; D003035:Cobalt; D008780:Methyltransferases; C060508:uroporphyrin-III C-methyltransferase; D014805:Vitamin B 12