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Summary:Porphyrin metabolism was investigated in a 63-year-old male patient who developed a subacute onset polyneuropathy with predominance of motor signs in the upper limb.The screening for lead, cadmium, mercury, aluminium and thallium was negative. The study of porphyrin metabolism showed remarkable abnormalities, particularly a very high level of plasmatic 5-aminolaevulinic acid contrasting with a normal level of porphobilinogen and a nearly complete loss of activity of aminolaevulinic acid dehydratase with no regenerative response to dithiothreitol or zinc ions. The other causes of aminolaevulinic acid dehydratase deficiency (tyrosinaemia, alcoholism, smoking, cirrhosis, renal insufficiency, diabetes mellitus) were ruled out.The diagnpsis of primary aminolaevulinic acid dehydratase deficiency was proposed and confirmed by the familial study, which revealed the existence of several heterozygous members in this family.

The properties of 9 ␦-aminolevulinate dehydratase (ALAD) mutants from patients with ALAD porphyria (ADP) were examined by bacterial expression of their complementary DNAs and by enzymologic and immunologic assays. ALADs were expressed as glutathione-S-transferase (GST) fusion proteins in Escherichia coli and purified by glutathioneaffinity column chromatography. The GST-ALAD fusion proteins were recognized by anti-ALAD antibodies and were enzymatically active as ALAD. The enzymatic activities of 3 ALAD mutants, K59N, A274T, and V153M, were 69.9%, 19.3%, and 41.0% of that of the wild-type ALAD, respectively, whereas 6 mutants, G133R, K59N/G133R, F12L, R240W, V275M, and delTC, showed little activity (< 8%). These variations generally reflect the phenotype of ALAD in vivo in patients with ADP and indicate that GST-ALAD fusion protein is indeed useful for predicting of the phenotype of ALAD mutants. The location of F12L mutation in the enzyme's molecular structure indicates that its disturbance of the quaternary contact of the ALAD dimer appears to have a significant influence on the enzymatic activity. Mouse monoclonal antibodies to human ALAD were developed that specifically recognized a carboxy terminal portion of ALAD, or other regions in the enzyme. This study represents the first complete analysis of 9 mutants of ALAD identified in ADP and indicates the highly heterogeneous nature of mutations in this disorder. IntroductionDelta-aminolevulinate dehydratase (ALAD) deficiency porphyria (ADP) is an autosomal recessive disorder caused by a homozygous ALAD deficiency. Patients with this condition have clinical symptoms of acute hepatic porphyria such as abdominal pain, vomiting, pain in the arms and legs, and neuropathy. ALAD is the second enzyme in the heme biosynthetic pathway. It catalyzes the Knorr-type condensation of 2 molecules of aminolevulinate acid (ALA) to form a monopyrrole, porphobilinogen (PBG). 1 This enzyme activity is present in large excess compared to other enzymes in the heme biosynthetic pathway, and its partial deficiency does not usually result in any clinical consequences. Seven patients with ADP have been reported to date, 2-6 though only 4 of them have been confirmed by immunochemical or molecular analysis. [2][3][4] Of these 4 cases, the first 2 were German patients reported by Doss and coworkers, 7 the third was a Swedish baby boy studied by Thunell and colleagues, 8 and the fourth was an elderly Belgian man reported by Hassoun and associates. 9 Recently, an asymptomatic Swedish baby girl has been identified to have a markedly decreased ALAD activity. 10 Thus far, a total of 9 point mutations of the alad gene have been identified in these 5 subjects, which resulted in different amino acid changes. However, the enzymatic activity of ALAD expressed by mutant ALAD was investigated only for 4 mutants, A274T and R240W, in German patient B, 3 and V153M and delTC in German patient H 11 (singleletter amino acid codes). This previous study with German patient B demonstrated that ALAD activity co...