A simplified method for determination of uroporphyrinogen decarboxylase activity in human blood.

The determination of erythrocyte uroporphyrinogen decarboxylase activity is essential for differentiating familial (type II) porphyria cutanea tarda from the sporadic (type I) form of the disease. A new technique for the determination of uroporphyrinogen decarboxylase activity in human blood is described. Haemolysate is incubated with uroporphyrinogen III as substrate. Uroporphyrinogen unconverted during the reaction is oxidised to uroporphyrin and measured directly as free acid by HPLC. The enzyme activity is then calculated from the amount of substrate consumed. The technique is simple, rapid and highly reproducible. It is recommended as a clinical assay.