Studies on porphobilinogen

Abstract

The changes occurring when porphobilinogen solns. were (a) heated at pH 5.2 and in HC1 and (b) allowed to stand at pH 1 were studied spectrophotometrically. The spectral absorption at 286-288m[mu] of porphobilinogen solns. as usually prepared was shown to be due to uric acid. Approx. 2[mu]g. of porphyrin per unit of porphobilinogen were obtained, the exact yield depending on the conditions of heating. A yellow pigment was formed on heating, which absorbed maximally at 480 m[mu]. It is suggested that this is a 5,5[image] -disubstituted, dipyrrylmethene or a bilene. On standing at pH 1 a violet pigment of unknown structure was formed which absorbed maximally at 503-505 m[mu]. It was not possible to separate a 2d-precursor from porphyria urines. The expts. reported, while not providing conclusive evidence, support the view that porphobilinogen itself can form porphyrin, yellow pigment and violet pigment according to the conditions.