Properties and inhibition of the first two enzymes of the non-mevalonate pathway of isoprenoid biosynthesis

Enzymes of the l-deoxy-D-xylulose 5-phosphate/2-C- methylerythritol 4-phosp hate (DOXP/MEP) pathway are targets for new herbicides and antibacterial dr ugs. Until now, no inhibitors for the DOXP synthase have been known of. We show that one of the breakdown products of the herbicide clomazone affects the DOXP synthase. One inhibitor of the non-mevalonate pathway, fosmidomyci n, blocks the DOXP reductoisomerase (DXR) of plants and bacteria. The I,, v alues of plants are, however, higher than those found for the DXR of Escher ichia coli. The DXR of plants, isolated from barley seedlings, shows a pH o ptimum of 8.1, which is typical for enzymes active in the chloroplast strom a.