High-performance liquid chromatography assay for 1-deoxy-d-xylulose 5-phosphate synthase activity using fluorescence detection

A high-performance liquid chromatography assay for activity of 1-deoxy-d-xylulose 5-phosphate synthase, an early enzyme in the recently discovered 2-C-methyl-d-erythritol-4-phosphate pathway, was developed. In this assay, the enzymatic product 1-deoxy-d-xylulose was first derivatized with a fluorescent reagent 2-anthranilic acid, followed by separation using HPLC on a Nova-Pak phenyl column with a mobile phase containing CH3CN–water–1-butylamine–tetrahydrofuran–H3PO4 (2:97:0.125:0.5:0.25, v/v). The eluate was monitored by fluorescence detection at an excitation wavelength of 320 nm and an emission wavelength of 425 nm for quantitation of the fluorescent derivative. A linear response was obtained between 5 and 200 ng of 1-deoxy-d-xylulose. This assay was successfully applied to measure the 1-deoxy-d-xylulose 5-phosphate synthase activity in a recombinant E. coli overexpressing dxs gene. It demonstrated that this assay is simple, sensitive and selective compared to the methods used at present.