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Porra, R. J. and Schäfer, W. and Cmiel, Edmund and Katheder, Ingrid and Scheer, Hugo (1993): Derivation of the formyl-group oxygen of chlorophyll b from molecular oxygen in greening leaves of a higher plant (Zea mays). In: FEBS Letters, Vol. 323, No. 1-2: pp. 31-34
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Abstract

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 131-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.