Molecular cloning and characterization of glucose-6-phosphate dehydrogenase from Brugia malayi.

Glucose-6-phosphate dehydrogenase (G6PD), a regulatory enzyme of the pentose phosphate pathway from Brugia malayi , was cloned, expressed and biochemically characterized. The Km values for glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (NADP) were 0·25 and 0·014 m m respectively. The rBmG6PD exhibited an optimum pH of 8·5 and temperature, 40 °C. Adenosine 5′ [ γ -thio] triphosphate (ATP- γ -S), adenosine 5′ [ β , γ -imido] triphosphate (ATP- β , γ -NH), adenosine 5′ [ β -thio] diphosphate (ADP- β -S), Na + , K + , Li + and Cu ++ ions were found to be strong inhibitors of rBmG6PD. The rBmG6PD, a tetramer with subunit molecular weight of 75 kDa contains 0·02 mol of SH group per mol of monomer. Blocking the SH group with SH-inhibitors, led to activation of rBmG6PD activity by N -ethylmaleimide. CD analysis indicated that rBmG6PD is composed of 37% α -helices and 26% β -sheets. The unfolding equilibrium of rBmG6PD with GdmCl/urea showed the triphasic unfolding pattern along with the highly stable intermediate obtained by GdmCl.