Biosynthesis of terpenoids:: 1-deoxy-D-xylulose-5-phosphate reductoisomerase from Escherichia coli is a class B dehydrogenase

1-Deoxy-D-xylulose-5-phosphate is converted into 2-C-methyl-D-erythritol-4-phosphate by the catalytic action of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (Dxr protein) using NADPH as cofactor, The stereochemical features of this reaction were investigated in in vitro experiments with the recombinant Dxr protein of Escherichia coli using (4R)- or (4S)-[4-H-2(1)]NADPH as coenzyme. The enzymatically formed 2-C-methyl-D-erythritol-4-phosphate was isolated and converted into 1,2:3,4-di-O-isopropylidene-2-C-methyl-D-erythritol; NMR spectroscopic investigation of this derivative indicated that only (4S)-[4-H-2(1)]NADPH affords 2-C-methyl-D-erythritol-4-phosphate labelled exclusively in the H-Re position of C-1, Stereospecific transfer of H-Si from C-4 of the cofactor identifies the Dxr protein of E, coli as a class B dehydrogenase, (C) 2000 Federation of European Biochemical Societies.