Porphyrins found in urine of patients with symptomatic porphyria.

The exact structure of the type-I11 isomer penta-, hexaand hepta-carboxylic porphyrinogens that are involved as intermediates in the conversion of uroporphyrinogen I11 into coproporphyrinogen 111 have been elucidated (Jackson et al., 1976). The corresponding porphyrins are to be found in the urine of patients suffering from the porphyrin-overproduction diseases symptomatic porphyria and congenital erythropoietic porphyria, together with the type-I isomers of these porphyrins. The faecal and urine extracts from symptomatic porphyric patients also contain isocoproporphyrins (Elder, 1974), which are not in the direct biosynthetic pathway and whose role, if any, is uncertain. It is possible, by usingt.1.c. (Smith, 1975; system A), toseparatecompletelyaporphyrin methyl ester band running between coproporphyrin and pentacarboxylic porphyrin methyl esters. This is the characteristic position for isocoproporphyrin methyl ester. This band was found in all urine extracts from 12 untreated cases of symptomatic porphyria. The RF value of this band did not coincide exactly with that of isocoproporphyrin methyl ester prepared from faecal extracts or by chemical synthesis, the RF value being slightly lower in all cases. Mass-spectrometry results also differed, giving a peak at 682 instead of the expected 710 mass units for isocoproporphyrin methyl ester. The visible and U.V. spectra were almost identical. By using a technique which decarboxylates acetate groups (Cornford & Benson, 1963) both porphyrins were converted into tricarboxylic porphyrins, suggesting that theporphyrin in urinealso belonged to the isocoproporphyrin series. A mol.wt. of 682 suggested a loss of an ethyl group by the isocoproporphyrin molecule to give desethylisocoproporphyrin. The suggested structure is shown in Fig. 1(a). A second band was found on t.1.c. plates from eight of the twelve urine extracts from patients with symptomatic porphyria running between the pentaand hexa-carboxylic methyl ester bands. It showed a deep cherry-red fluorescence in U.V. light with a Soret