Figure 5.

Stability of glucose-6-phosphate dehydrogenases (G6PDs) incubated with different concentrations of Gdn-HCl and inactivation assays. (A) Effects of Gdn-HCl on the activity of WT G6PD and the G6PD Zacatecas, Vanua-Lava and Viangchan mutants. All the enzymes were incubated at 0.2 mg/mL in 50 mM phosphate buffer pH 7.35 in the presence of the indicated concentrations of Gdn-HCl for 2 h at 37 °C; (B) Inactivation of WT G6PD and the mutants by 0.25 M at 37 °C. At the indicated times, aliquots were withdrawn from the samples and assayed for residual activity. In both assays, residual activity was expressed as a percentage of the activity for the same sample measured at 25 °C without Gdn-HCl and all enzymes were prepared and diluted immediately before used. Both assays were performed in duplicate; standard errors were less than 5%.