Isolation of the dxr gene of Zymomonas mobilis and characterization of the 1-deoxy-D-xylulose 5-phosphate reductoisomerase

The gene encoding the second enzyme of the 2C-methyl-D-erythritol 4-phosphate (MEP) pathway for isopentenyl diphosphate biosynthesis, 1-deoxy-D-xylulose 5-phosphate (DXP) reductoisomerase, was cloned and sequenced from Zymomonas mobilis. The deduced amino acid sequence showed the highest identity (48.2%) to the DXP reductoisomerase of Escherichia coli. Biochemical characterization of the purified DXP reductoisomerase showed a strict dependence of the enzyme on NADPH and divalent cations (Mn(2+), Co(2+) or Mg(2+)). The enzyme is a dimer with a molecular mass of 39 kDa per subunit and has a specific activity of 19.5 U mg protein(-1). Catalysis of the intramolecular rearrangement and reduction of DXP to MEP is competitively inhibited by the antibiotic fosmidomycin with a K(i) of 0.6 microM.