In the acute porphyrias (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and the very rare delta-aminolevulinic acid dehydratase ALAD-d porphyria), the characteristic severe neurovisceral involvement is mainly ascribed to a tissue accumulation of delta-aminolevulinic acid, a neurotoxic nonporphyrin precursor.
delta-Aminolevulinate dehydratase deficient porphyria, a recently recognized inborn error of heme biosynthesis, results from the markedly deficient activity of the heme biosynthetic enzyme, delta-aminolevulinate dehydratase (ALA-D).
Deficient porphobilinogen-synthase (PBG-S) of a previously reported patient with PBG-S defect porphyria (red cell PBG-S activity approximately 2% of the physiological level) has been characterized in erythrocytes after DEAE cellulose chromatography, ultrafiltration and polyacrylamide gel electrophoresis: Residual specific activity of 2.5%, increase of Km, but identical fractionation, concentration and electrophoretic mobility of the enzyme protein compared to controls.