Characterization of Burkholderia glumae BGR1 4-Hydroxy-3-methylbut-2-enyl Diphosphate Reductase (HDR), the Terminal Enzyme in 2-C-Methyl-D-erythritol 4-Phosphate (MEP) Pathway

Abstract

4-Hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR) is the ultimate enzyme in 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway converting (E)-4-hydroxy-3-methylbut-2-enyl pyrophosphate (HMBPP) into isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Burkholderia glumae, a Gram-negative rice-pathogenic bacterium, harbors 2 hdr genes and lacks isopentenyl diphosphate isomerase (idi). Both HDR enzymes could complement E. coli hdr deletion mutant (DYTL1). Both of the recombinant BDR proteins, BgHDR1 and BgHDR2, catalyzed reduction of HMBPP into IPP and DMAPP at a ratio of 2:1, in contrast to 5:1 ratio of other bacterial HDRs so far characterized. The k(cat) and K-m values of BgHDR1 and BgHDR2 were 187.0 min(-1) and 6.0 mu M and 66.6 min(-1) and 21.2 mu M, respectively. Physiological significance of the kinetic properties was discussed.