Molecular cloning and nucleotide sequence of cDNA for human glucose-6-phosphate dehydrogenase variant A(-)

Glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ oxidoreductase, EC 1.1.1.49) A(-) is a common variant in Blacks that causes sensitivity to drug-and infection-induced hemolytic anemia. A cDNA library was constructed from Epstein-Barr virus-transformed lymphoblastoid cells from a male who was G6PD A(-). One of four cDNA clones isolated contained a sequence not found in the other clones nor in the published cDNA sequence. Consisting of 138 bases and coding 46 amino acids, this segment of cDNA apparently is derived from the alternative splicing involving the 3' end of intron 7. Comparison of the remaining sequences of these clones with the published sequence revealed three nucleotide substitutions: C33----G, G202----A, and A376----G. Each change produces a new restriction site. Genomic DNA from five G6PD A(-) individuals was amplified by the polymerase chain reaction. The base substitution at position 376, identical to the substitution that has been reported in G6PD A(+), was present in all G6PD A(-) samples and none of the control G6PD B(+) samples examined. The substitution at position 202 was found in four of the five G6PD A(-) samples and no normal control sample. At position 33 guanine was found in all G6PD A(-) samples and seven G6PD B(+) control samples and is, presumably, the usual nucleotide found at this position. The finding of the same mutation in G6PD A(-) as is found in G6PD A(+) strongly suggests that the G6PD A(-) mutation arose in an individual with G6PD A(+), adding another mutation that causes the in vivo instability of this enzyme protein.