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Brazilian Journal of Medical and Biological Research
On-line version ISSN 1414-431X
LEITE, A.A. and BARRETTO, O.C. de O.. Erythrocyte glucose-6-phosphate dehydrogenase activity assay and affinity for its substrate under "physiological" conditions. Braz J Med Biol Res [online]. 1998, vol.31, n.12, pp.1533-1535. ISSN 1414-431X. http://dx.doi.org/10.1590/S0100-879X1998001200004.
Glucose-6-phosphate dehydrogenase (G6PD) activity and the affinity for its substrate glucose-6-phosphate were investigated under conditions similar to the physiological environment in terms of ionic strength (I: 0.188), cation concentration, pH 7.34, and temperature (37oC). A 12.4, 10.4 and 21.4% decrease was observed in G6PD B, G6PD A+ and G6PD A- activities, respectively. A Km increase of 95.1, 94.4 and 95.4% was observed in G6PD B, G6PD A+ and G6PD A-, respectively, leading to a marked decrease in affinity. In conclusion, the observation of the reduced activity and affinity for its natural substrate reflects the actual pentose pathway rate. It also suggests a much lower NADPH generation, which is crucial mostly in G6PD-deficient individuals, whose NADPH availability is poor.
Keywords : glucose-6-phosphate dehydrogenase; red blood cells; G6PD activity and affinity.