Anaerobic breakdown of uroporphyrins I and III to bile pigments by extracts of Clostridium tetanomorphum.

Two blue bile pigments were formed under anaerobic conditions from the tetrapyrrole precursor delta-aminolevulinate by cells and cell extracts of Clostridium tetanomorphum. These compounds were also formed by cell extracts from the octacarboxylic tetrapyrrole, uroporphyrin III. Bactobilin, the first bacterial bile pigment to be discovered, is related to uroporphyrin I. The present results hence increase the number of bile pigments related to bactobilin. Bactobilin and its isomers differ markedly from the eukaryotic bile pigments which are all related to the dicarboxylic compound, protoporphyrin IX. The enzyme participating in the formation of the bacterial bile pigments was obligatorily anaerobic, in decided contrast to the only other known bile pigment-forming enzyme, the eukaryotic oxygen-requiring heme oxygenase.