DXP reductoisomerase (1-deoxy-D-xylulose 5-phosphate reductoisomerase or DXR) is an enzyme that interconverts 1-deoxy-D-xylulose 5-phosphate (DXP) and 2-C-methyl-D-erythritol 4-phosphate (MEP).

DXR is part of the MEP pathway (nonmevalonate pathway) of isoprenoid precursor biosynthesis.

This enzyme is required for terpenoid biosynthesis in some organisms, since it is a key enzyme on the MEP pathway for the production of the isoprenoid precursors IPP and DMAPP.

[1] In Arabidopsis thaliana 1-deoxy-D-xylulose 5-phosphate reductoisomerase is the first committed enzyme of the MEP pathway for isoprenoid precursor biosynthesis.

The enzyme requires Mn2+, Co2+ or Mg2+ for activity, with Mn2+ being most effective.