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.
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.
Porra
R J
RJ
Botanisches Institut der Universität München, Germany.
Schäfer
W
W
Katheder
I
I
Scheer
H
H
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*
D001429:Bacteriochlorophylls; D014867:Water; D010100:Oxygen