Verdohemochrome IX alpha: preparation and oxidoreductive cleavage to biliverdin IX alpha.

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Abstract
Several studies have shown that both terminal oxygen atoms of biliverdin are derived from molecular oxygen. Since the conversion of verdohemochrome to biliverdin has been assumed to be hydrolytic, these findings seemed to exclude verdohemochrome as an intermediate in the degradation of heme to biliverdin. Coupled oxidation of (horse heart) myoglobin and ascorbate yielded a pure preparation of verdohemochrome IX.alpha.. The structure and ferrous state of this product were determined from its composition, ligand reactions, 1H NMR spectrum and conversion to biliverdin IX.alpha. dimethyl ester. Reaction with ascorbate and 18O2 converted this compound to biliverdin that contained an atom of 18O. Successive treatment of verdohemochrome, first oxidation with H2O2 and then reduction with phenylhydrazine, yielded the Fe complex of biliverdin. Thus, hydrolysis is not an obligatory step in the conversion of verdohemochrome to biliverdin. Heme can be converted, with verdohemochrome as an intermediate, into biliverdin in which the 2 terminal oxygen atoms are derived from different O2 molecules.