Mg-2,4-divinyl pheoporphyrin a5: the product of a reaction catalyzed in vitro by developing chloroplasts

The major product of an aerobic reaction mixture containing developing chloroplasts, Mg-protoporphyrin IX, S-adenosylmethionine, and other cofactors was isolated and purified. Structural studies using nuclear magnetic resonance confirmed earlier reports, based on fluorescence and absorption spectra, that this compound is Mg-2,4-divinyl pheoporphyrin a5. The molecular weight determined by secondary-ion mass spectroscopy further confirmed the assigned structure. Absorption and fluorescence spectra indicate that this compound is identical to that reported previously by various workers in less-purified biological extracts. The nuclear magnetic resonance spectrum of the Mg-free base also supports the assigned structure.