Bases moléculaires des maladies enzymatiques génétiques

Partial characterization of the inactive mutant form of human red cell bisphosphoglyceromutase and comparison with an alkylated form

The trifunctional enzyme bisphosphoglyceromutase (or diphosphoglycerate mutase) (EC 2.7.5.4) was purified from human red cells and injected into two chickens. Specific anti-bisphosphoglyceromutase antibodies were produced that displayed a single precipitation line on Ouchterlony plates and on immunoelectrophoresis. No cross-reaction of these antibodies was detected with phosphoglyceromutase, the common glycolytic enzyme. Immunoneutralization of bisphosphoglyceromutase and of its two other activities, i.e., bisphosphoglycerate phosphatase and phosphoglyceromutase, was observed for a purified preparation. The anti-bisphosphoglyceromutase antibody reacts with the inactive enzyme present in the hemolysate of a mutant human subject. It also binds bisphosphoglyceromutase inactivated by N-ethylmaleimide, a strong alkylating agent of SH groups. Active bisphosphoglyceromutase is stable at 55 degrees C, whereas the inactive forms of the mutant and of the alkylated hemolysates are thermolabile. These forms can be protected against thermal precipitation by 4 mM 2,3-diphosphoglycerate and 4 mM 3-phosphoglycerate. These findings afford evidence that the binding of the substrates on the bisphosphoglyceromutase molecule is not prevented by alkylation nor by the mutation of the hereditary inactive enzyme.

Quantitative variations of red-cell cytochrome b5 reductase (NADH-methemoglobin-reductase) in the Algerian population: evidence for defective alleles

A striking proportion of Algerian subjects was reported among patients with congenital recessive methemoglobinemia due to cytochrome b5 reductase deficiency (Kaplan et al. 1979). A population survey was carried out in red blood cells from 1000 Algerian subjects. In 16 subjects, the cytochrome b2 reductase activity was diminished by 50%. Family studies indicated the presence of a defective allele with an overall gene frequency of 0.008. Immunologically cross-reacting material was found in red cells with low cytochrome b5 reductase activity. Leukocytes exhibited normal levels of enzyme in some families and low levels in others suggesting that at least two different deficient alleles at the DIA1 locus were present in the Algerian population. A higher prevalence of the deficient allele(s) was found in subjects of Kabyle origin.