Porphyrin biosynthesis from prophobilinogen by duck blood hemolysate

The formation of porphyrins from porphobilinogen by a duck blood hemolysate was examined. The system was found to form mainly protoporphyrin IX and hemin, and accumulated lesser amounts of uroporphyrins, hepatacarboxylic porphyrin, and coproporphyrins. By storage at -20 degrees the accumulation of uroporphyrins and heptacarboxylic porphyrin was increased. Both porphyrins were mainly the type III isomers. By addition of dithiothreitol the porphyrin pattern reversed to the original one formed by the fresh hemolysate. Addition of a number of amines also inhibited the decarboxylating system without affecting the original isomer distribution among the porphyrins. Addition of Fe2+ (3mM) did not affect the porphyrin pattern or the isomer distribution. Addition of Pb2+ (2.5 mM) partially inhibited the decarboxylating system, whereas at higher concentrations (4 mM) it increased the decarboxylation rate of the heptacarboxylic porphyrin. The obtained results are discussed in relation to porphyrin accumulation in porphyria cutanea tarda and in acquired hepatic porphyrias.