Synthesis, biochemical, and biological evaluation of C2 linkage derivatives of amino sugars, inhibitors of glucokinase from Trypanosoma cruzi

Eighteen amino sugar analogues were screened against Trypanosoma cruzi glucokinase (TcGlcK), a potential drugtarget of the protozoan parasite in order to assess for viable enzyme inhibition. The analogues were divided into three amino sugar scaffolds that included D-glucosamine (D-GlcN), D-mannosamine (D-ManN), and D-galactosamine (D-GalN); moreover, all but one of these compounds were novel. TcGlcK is an important metabolic enzyme that has a role in producing G6P for glycolysis and the pentose phosphate pathway (PPP). The inhibition of these pathways via glucose kinases (i.e., glucokinase and hexokinase) appears to be a strategic approach for drug discovery. Glucose kinases phosphorylate D-glucose with co-substrate ATP to yield G6P and the formed G6P enters both pathways for catabolism. The compound screen revealed five on-target confirmed inhibitors that were all from the D-GlcN series, such as compounds 1, 2, 4, 5, and 6. Four of these compounds were strong TcGlcK inhibitors (1, 2, 4, and 6) since they were found to have micromolar inhibitory constant (Ki) values around 20 mu M. Three of the on-target confirmed inhibitors (1, 5, and 6) revealed notable in vitro anti-T. cruzi activity with IC50 values being less than 50 mu M. Compound 1 was benzoyl glucosamine (BENZ-GlcN), a known TcGlcK inhibitor that was the starting point for the design of the compounds in this study; in addition, TcGlcK - compound 1 inhibition properties were previously determined [D'Antonio, E. L. et al. (2015) Mol. Biochem. Parasitol. 204, 64-76]. As such, compounds 5 and 6 were further evaluated biochemically, where formal Ki values were determined as well as their mode of TcGlcK inhibition. The Ki values determined for compounds 5 and 6 were 107 +/- 4 mu M and 15.2 +/- 3.3 mu M, respectively, and both of these compounds exhibited the competitive inhibition mode.

Automated summary

The screening of eighteen amino sugar analogues against Trypanosoma cruzi glucokinase revealed five on-target confirmed inhibitors, all from the D-GlcN series. Four of these compounds were identified as strong TcGlcK inhibitors, while three showed significant in vitro anti-T. cruzi activity. Compounds 5 and 6 were further evaluated biochemically, with formal Ki values determined and exhibiting competitive inhibition mode for TcGlcK.