Negro variant of glucose-6-phosphate dehydrogenase deficiency (A-) in man

Glucose-6-phosphate dehydrogenase in erythrocytes of the Negro type associated with enzyme deficiency (A(-)) was separated by chromatography on a carboxymethyl-Sephadex column from the electrophoretically indistinguishable Negro variant with normal enzyme activity (A(+)). Quantitative immunologic neutralization tests indicated that the A(-) enzyme had about the same enzymatic and serological activity as the A(+) and the normal (B(+)) enzymes. The enzyme activity of the A(-) variant in young erythrocytes was similar to that in young cells from normal individuals, although the activity of the A(-) variant in unfractionated red cells was 10 to 15 percent of normal. These data indicate that the basic defect in the variant enzyme (A(-)) is a structural mutation which causes more rapid degradation of the enzyme during erythrocyte aging.