Hereditary hepatic porphyria with delta aminolevulinate dehydrase deficiency: Immunologic characterization of the non-catalytic enzyme

Abstract

Immunoreactive delta-aminolevulinate dehydrase (ALA-D) was measured in lysates from two porphyric patients with ALA-D deficiency (enzyme activities were below 2% of the normal level). By using two different immunologic methods, we found a cross-reactive immunologic material (CRIM+) which corresponded to 20% and 33% of the control level. Therefore the molecular basis that accounts for the deficiency of ALA-D in these patients is a structurally modified enzyme. The methods used to determine the molecular weight (by Western blotting) and the isoelectric point (by chromatofocusing) of the mutants did not show any difference by comparison with the normal enzyme.

Cloning and expression of the defective genes from a patient with delta-aminolevulinate dehydratase porphyria.

“…The patient had ALAD activity less than 3% of normal controls, both in erythrocytes (8) and in lymphocytes (9). Immunochemical studies showed that the proband's cells contained 20% positive crossreactive immunological material (CRIM) (25), suggesting the existence of a structurally altered enzyme(s). Northern blot analysis using total RNA showed a normal size and a normal amount of ALAD mRNA (data not shown).…”

“…Previous studies indicated that ALAD activity in the proband's cells was less than 3% ofnormal (8,9), which accounted for the marked elevation of urinary ALA excretion in him (4). ALAD protein content in the proband's cells was markedly reduced, but a significant amount of CRIM was also present, suggesting that a noncatalytic enzyme was expressed (25). In the original description ofthis patient (8), he was considered to be homozygous for ALAD deficiency, since ALAD activity in erythrocytes was extremely low (; 2%), and the parents and the siblings had enzyme activity in the range of 50% of normal (8).…”

Biochemical Diagnosis of an Hereditary Aminolaevulinate Dehydratase Deflciency in a 63-Year-Old Man

“…The immunological characterization of the two patients of Doss showed a cross-reactive immunological material which corresponded to 20% and 33% of the control level (33). Therefore the molecular basis for the deficiency of aminolaevulinic acid dehydratase in these patients is a structurally modified enzyme (33).…”

“…In the patient of Thunell, the immunoreactive enzyme protein in the child's erythrocytes was decreased to 28% of the normal control, suggesting the presence of positive cross reactive material (34). These results suggest that in these cases, the aminolaevulinic acid dehydratase deficiency is associated with the production of a catalytically abnormal enzyme protein (33,34).…”

“…Therefore the molecular basis for the deficiency of aminolaevulinic acid dehydratase in these patients is a structurally modified enzyme (33). The methods used to determine the relative molecular mass (by Western blotting) and the isoelectric point (by chromatofocusing) of the mutants revealed no differences between the modified and normal enzymes (33). In the patient of Thunell, the immunoreactive enzyme protein in the child's erythrocytes was decreased to 28% of the normal control, suggesting the presence of positive cross reactive material (34).…”