Biochemical Defects in Two Types of Human Hepatic Porphyria

Abstract

In a patient with hereditary coproporphyria, increased enzymatic synthesis of δ-aminolevulinic acid (ALA) in the liver contributed to the increased excretion of porphyrins and their precursors. A similar enzymatic abnormality has been found in acute intermittent porphyria. By contrast, in a patient with porphyria cutanea tarda, despite massive porphyrinuria, hepatic ALA synthetase was not detectably elevated. Additional experimental data indicate that heme participates in the feedback regulation of ALA synthetase.