Pentacarboxylic intermediates in haem biosynthesis

The incorporation of the four possible type III porphyrinogens into protoporphyrin is described and their various rates or conversion are discussed. The techniques used involved the incubation of the porphyrinogens in chicken red cell haemolysates followed by extraction and characterisation of the end products on HPLC and TLC. Porphyrin 5 b c d was shown to be more slowly incorporated than porphyrins 5 a b d, 5 a c d and 5 a b c. The relevance of these findings to an understanding of the porphyrin excretion pattern in hepato-erythrocitic porphyria is considered.