title: The derivation of the oxygen atoms of the 13(1)-oxo and 3-acetyl groups of bacteriochlorophyll a from water in Rhodobacter sphaeroides cells adapting from respiratory to photosynthetic conditions: evidence for an anaerobic pathway for the formation of isocyclic ring E.
abstract: Using mass spectrometry, we have demonstrated 18O-labelling of both the 13(1)-oxo and 3-acetyl groups of newly-formed bacteriochlorophyll a synthesized by Rhodobacter sphaeroides cells during adaptation from respiratory to photosynthetic conditions in the presence of H218O. This derivation of the 13(1)-oxo group of bacteriochlorophyll a from water provides a stark contrast with that of chlorophylls in higher plants where ring E formation is an aerobic process in which the 13(1)-oxo group arises from molecular oxygen via an oxygenase activity. The formation of the 3-acetyl group of bacteriochlorophyll a, however, is consistent with the enzymic hydration of the 3-vinyl group of a derivative of chlorophyll a.
authors.affiliation: Botanisches Institut der Universität München, Germany.
authors.forename: R J
authors.initials: RJ
authors.lastname: Porra
authors.forename: W
authors.initials: W
authors.lastname: Schäfer
authors.forename: I
authors.initials: I
authors.lastname: Katheder
authors.forename: H
authors.initials: H
authors.lastname: Scheer
mesh_terms: D000693:Anaerobiosis; D001429:Bacteriochlorophylls / Q000096:biosynthesis / Q000737:chemistry*; D013058:Mass Spectrometry; D010100:Oxygen / Q000737:chemistry*; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D001429:Bacteriochlorophylls; D014867:Water; D010100:Oxygen