The Enzymatic Defect in Variegate Porphyria

Abstract

Fecal protoporphyrin is increased in patients with variegate porphyria, even during clinical remission, suggesting an enzymatic defect in the terminal portion of the heme biosynthetic pathway. We measured the activities of protoporphyrinogen oxidase, which catalyzes the oxidation of protoporphyrinogen to protoporphyrin, and heme synthase, which catalyzes the chelation of iron to protoporphyrin, in cultured skin fibroblasts from five normal controls and five patients with variegate porphyria.