Isolation of Human Ferrochelatase

To the Editor.— Ferrochelatase (protoheme ferrolyase, EC 4.99.1.1) catalyzes the insertion of ferrous iron into protoporphyrin IX to form protoheme. Reduced activity of this enzyme is found in the human disease erythropoietic protoporphyria, which is characterized by high levels of protoporphyrin in blood, stool, and skin, and extreme sensitivity to visible light. 1 Although treatment with β-carotene relieves photosensitivity in the majority of patients, 1 it has no effect on the abnormal accumulation of protoporphyrin. Purification of human ferrochelatase is the necessary first step in studies of thegenetic defect of this disease. Ferrochelatase has been isolated from rat and beef liver and chicken erythrocytes. 2-5 We report here that we have been able to isolate ferrochelatase from human liver obtained at autopsy, using the methods published for the isolation of rat liver ferrochelatase. 2 Table 1 summarizes the purification scheme. The yields and purity of the enzyme are similar