Derivation of the formyl-group oxygen of chlorophyll b from molecular oxygen in greening leaves of a higher plant (Zea mays).
Using mass spectroscopy, we demonstrate as much as 93% enrichment of the 7-formyl group oxygen of chlorophyll b when dark-grown, etiolated maize leaves are greened under white light in the presence of 18O2. This suggests that a mono-oxygenase is involved in the oxidation of its methyl group precursor. The concomitant enrichment of about 75% of the 13(1)-oxygen confirms the well-documented finding that this oxo group, in both chlorophyll a and b, also arises from O2. High 18O enrichment into the 7-formyl oxygen relative to the substrate 18O2 was achieved by optimization of the greening conditions in combination with a reductive extraction procedure. It indicates not only a single pathway for Chl b formyl group formation, but also unequivocally demonstrates that molecular oxygen is the sole precursor of the 7-formyl oxygen.
Porra
R J
RJ
Botanisches Institut der Universität, München, Germany.
Schäfer
W
W
Cmiel
E
E
Katheder
I
I
Scheer
H
H
D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D013058:Mass Spectrometry; D006899:Mixed Function Oxygenases / Q000378:metabolism; D015394:Molecular Structure; D010100:Oxygen / Q000378:metabolism*; D003313:Zea mays / Q000378:metabolism*
D002734:Chlorophyll; C037184:chlorophyll b; D006899:Mixed Function Oxygenases; D010100:Oxygen; D000077194:Chlorophyll A