Synthesis and evaluation of 1-deoxy-D-xylulose 5-phosphoric acid analogues as alternate substrates for methylerythritol phosphate synthase

[GRAPHICS] Four deoxyxylulose phosphate (DXP) analogues were synthesized and evaluated as substrates/ inhibitors for methylerythritol phosphate (MEP) synthase. In analogues CF3-DXP (1), CF2-DXP (2), and CF-DXP (3), the three methyl hydrogens at Cl of DXP were sequentially replaced by fluorine. In the fourth analogue, Et-DXP (4), the methyl group in DXP was replaced by an ethyl moiety. Analogues 1, 2, and 4 were not substrates for MEP synthase under normal catalytic conditions and were instead modest inhibitors with IC50 values of 2.0, 3.4, and 6.2 mM, respectively. In contrast, 3 was a good substrate (k(cat) = 38 s(-1), K-m = 227 mu M) with a turnover rate similar to that of the natural substrate. These results are consistent with a retro-aldol/aldol mechanism rather than an a-ketol rearrangement for the enzyme-catalyzed conversion of DXP to MEP.