Biochemical characterization of highly active Trypanosoma brucei gambiense glycerol kinase, a promising drug target

Human African trypanosomes are blood parasites that cause sleeping sickness, a debilitating disease in sub-Saharan Africa. Glycerol kinase (GK) of these parasites additionally possesses a novel property of reverse catalysis. GK is essential to blood stream form trypanosome, and therefore a promising drug target. Here, utilizing recombinant DNA technology an optimized procedure for obtaining large amount of the purified protein was established. Furthermore, biochemical data on its enzymology are reported. The protein was maximally active at pH 6.8 over a temperature range of 25-70 degrees C, with activation energy of 34.02 +/- 0.31 kJ mol(-1). The enzyme catalyses a reversible bisubstrate [ADP and glycerol 3-phosphate (G3P)]-biproduct (ATP and glycerol) reaction. It has K-m of 0.90 and 5.54 mM for ADP and G3P, respectively, and V-max of 25.3 and 20.0 mu mol min(-1) mg(-1), respectively. Unexpectedly, the enzyme lost more than 50% of its activity in 48 h at 4 degrees C in 0.1 M sodium phosphate buffer pH 6.8 containing 10 mM MgSO4. However, perfect stabilization of the GK for more than 4 weeks was achieved in the presence of its natural ligands and cofactor. Using this stabilized protein, crystals of trypanosome GK with better resolution were obtained. This will accelerate the success of GK inhibitor development for drug design.