Porphobilinogen oxygenase from human erythrocytes

Porphobilinogen oxygenase was isolated from red cells of healthy persons and of patients with disturbances in porphyrin metabolism. The hemolysates were purified by DEAE-cellulose chromatography and the oxygenase was eluted with either 3 mmol/l phosphate buffer (pH 7.4) or with 10 mmol/l Tris-HCl buffer (pH 7.6). The oxygenase can also be isolated by filtration of the hemolysate through Sephadex G-100. In healthy persons a mean value of 84.1 +/- 29.7 nmol of porphobilinogen consumed in 30 min per ml of blood was obtained. In patients with hepatic porphyrias (acute intermittent porphyria and porphyria cutanea tarda) the activity of porphobilinogen oxygenase was very low. In the case with acute intermittent porphyria the activity was increased when measured after storage at 4 degrees C but never reached normal values. In the cases of porphyria cutanea tarda, oxygenase activity increased after recovery and reached normal values. In patients with erythropoietic porphyria and in anemias the activity of porphobilinogen oxygenase gave high values. The erythrocyte enzyme was found to be heterogeneous when compared with the enzyme of other sources. It was only partially succinylated and was inactivated after storage for a few days at 4 degrees C. Some preparations showed the usual allosteric kinetics (n = 1.6--2.0), although Michaelian kinetics were also often observed. The enzyme was inhibited by alpha, alpha'-dipyridyl and EDTA as well as by several metals.