Enhancement of Bacterial Porphyrin Biosynthesis by Exogenous Aminolevulinic Acid and Isomer Specificity of the Products

5-Aminolevulinic acid (ALA) added to cultures of Pseodomonas leads to enhanced biosynthesis of porphyrins whereby metabolites are secreted directly into the medium. The total amount of secreted porphyrins increases with increasing ALA concentration up to ca. 2 mM, beyond which ALA becomes toxic to the cells. At 2 mM ALA, the predominant product secreted is uroporphyrin. Other porphyrins can be isolated including coproporphyrin and the decarboxylation metabolites in between uroporphyrin and coproporphyrin, as well as variable amounts of the zinc and copper chelates of these. After conversion to methyl ester derivatives and purification by HPLC, uroporphyrin. coproporphyrin, and esters of some of the intermediates were examined by NMR. In six strains examined, it was found that the majority of secreted uroporphyrin was the type I isomer. The coproporphyrin on the other hand ranged from pure coproporphyrin III in some strains to variable mixtures of the I and III isomers in others.