Red cell glucose-6-phosphate dehydrogenase deficiency in Finland. Characterization of a new variant with severe enzyme deficiency

Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency in Greek newborns: the Mediterranean C563T mutation screening

Glucose-6-Phosphate Dehydrogenase (G6PD) gene is located at the X-chromosome at Xq28 and the disease is recessively inherited predominantly in males. More than 400 variants have been proposed based on clinical and enzymatic studies. The aim of the current study was to identify C563T mutation in G6PD-deficient newborns and to correlate the enzyme residual activity with the presence of the mutation. Some 1189 full-term neonates aged 3-5 days old were tested for G6PD activity in dried blood spots from Guthrie cards using a commercial kit. DNA extraction from Guthrie cards and mutation identification among the deficient samples were performed with current techniques. A total of 92 (7.7%) newborns were G6PD-deficient. In 46 (50%), the mutation C563T was identified. The residual activity in C563T hemizygote males (n = 28) was statistically significantly lower (1.23 ± 0.93 U/g Hb) than that in non-C563T G6PD-deficient males (n = 25) (4.01 ± 1.20 U/g Hb, p < 0.0001) and in controls (13.6 ± 2.9 U/g Hb, p < 0.0001). In C563T heterozygote females, the estimated enzyme activity was lower than that determined in non-C563T females. Male C563T hemizygotes suffer from G6PD deficiency and severe neonatal jaundice. G6PD activity showed statistically significant correlation with total bilirubin blood levels.

Three-dimensional modeling of glucose-6-phosphate dehydrogenase-deficient variants from German ancestry

BACKGROUND

Loss of function of dimeric glucose-6-phosphate dehydrogenase (G6PD) represents the most common inborn error of metabolism throughout the world affecting an estimated 400 million people. In Germany, this enzymopathy is very rare.

METHODOLOGY/PRINCIPAL FINDINGS

On the basis of G6PD crystal structures, we have analyzed six G6PD variants of German ancestry by three-dimensional modeling. All mutations present in the German population are either close to one of the three G6P or NADP(+) units or to the interface of the two monomers. Two of the three mutated amino acids of G6PD Vancouver are closer to the binding site of NADP(+). The G6PD Aachen mutation is also closer to the second NADP(+) unit. The G6PD Wayne mutation is closer to the G6P binding region. These mutations may affect the binding of G6P and NADP(+) units. Three mutations, i.e. G6PD Munich, G6PD Riverside and G6PD Gastonia, lie closer to the interface of the two monomers. These may also affect the interface of two monomers.

CONCLUSION

None of these G6PD variants share mutations with the common G6PD variants known from the Mediterranean, Near East, or Africa indicating that they have developed independently. The G6PD variants have been compared with mutants from other populations and the implications for survival of G6PD variants from natural selection have been discussed.

Chronic non-spherocytic haemolytic disorders associated with glucose-6-phosphate dehydrogenase variants

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in over 400 million people world wide. In a small number of cases, G6PD deficiency can lead to mild-to-severe chronic haemolysis, which is further exacerbated by oxidative stress. Such G6PD variants have been described all over the world and are responsible for chronic non-spherocytic haemolytic anaemia (CNSHA). To date 61 G6PD molecular variants associated with CNSHA have been identified, only some of which can cause the severe reduction in stability of the red blood cell enzyme. The distribution of the different mutations shows a predominance of small mutational events, and many have been found repeatedly in different parts of the world. By revisiting the 61 class I variants described so far, we can observe that a low inhibition constant (Ki) for NADPH, a higher Km for substrates and a reduced thermostability are common.

Molecular characterization of a German variant of glucose-6-phosphate dehydrogenase deficiency (G6PD Aachen)

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-chromosome-linked hereditary disorder. Clinically, patients with G6PD deficiency often present with drug- or food-induced hemolytic crises or neonatal jaundice. G6PD is involved in the generation of NADPH and reduced glutathione. In contrast to American, Mediterranean, and African ancestries, only few variants are known from Middle and Northern Europe. We describe the molecular characterization of a distinct variant from the northwestern area of Germany, G6PD Aachen. The sequence of the G6PD gene from three afflicted males was found to be hemizygous at cDNA residue 1089 for a C-->G mutation with a predicted amino acid change of Asn363Lys. The 1089 C-->G point mutation is unique, but produces the identical amino acid change found in a Mexican variant of G6PD deficiency, G6PD Loma Linda. This G6PD-deficient variant is caused by a 1089 C-->A mutation. The 363-amino-acid replacement is located outside a known mutation cluster region between amino acid residues 380 and 450, but may disrupt or weaken dimer interactions of G6PD enzyme subunits.

Membrane characteristics and metabolic properties of glucose-6-phosphate dehydrogenase deficient red cells

Two Finnish variants of reduced erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) activity were studied. The G-6-PD Espoo variant is characterized by severe enzyme deficiency which is normally non-haemolytic although primaquine sensitive. The other variant, G-6-PD Helsinki, in which the enzyme activity is moderately reduced, is associated with chronic haemolytic anaemia. The activity of the pentose phosphate pathway was not stimulated by methylene blue in G-6-PD Espoo cells, whereas in normal and G-6-PD Helsinki cells there were increases in shunt activity of 64.5- and 5.3-fold, respectively. As judged by the accumulation of 6-phosphogluconate after incubation with 6-aminonicotinamide, the activity of the pentose phosphate pathway was similar in normal and G-6-PD Helsinki cells, whereas in G-6-PD Espoo cells the metabolic flux through this pathway was decreased. Quantities of sulphydryl groups in intact cells and isolated membranes were similar in normal and G-6-PD deficient cells, as revealed by spin label experiments. In contrast to the situation in normal cells, sulphydryl groups in G-6-PD Espoo cells, and to a lesser extent in G-6-PD Helsinki cells, were sensitive to oxidation by acetylphenylhydrazine. In the G-6-PD Helsinki cells, but not in the G-6-PD Espoo cells, membrane fluidity was increased, as judged from the increased mobility of the stearic acid spin label. Mechanisms are discussed by which G-6-PD deficient cells retain adequate levels of NADPH during resting conditions, and it is suggested that the chronic haemolysis associated with G-6-PD Helsinki could be due to a defect in the lipid region of the cell membrane.

Glucose-6-phosphate dehydrogenase deficiency in a native Danish family. A new variant

Deficiency of red cell glucose-6-phosphate dehydrogenase was found in a native Danish family, in which 2 boys suffered from severe haemolytic anaemia. The mother and 3 sisters of the boys were heterozygotes for G-6-PD deficiency. The biochemical investigations indicate that this deficient G-6-PD is very similar to the Mediterranean variant; however, this variant gene may represent another example of G-6-PD 'Helsinki' or an unique variant with properties similar to G-6-PD B(--).