FARNESYL-DIPHOSPHATE SYNTHASE - INTERPLAY BETWEEN SUBSTRATE TOPOLOGY, STEREOCHEMISTRY, AND REGIOCHEMISTRY IN ELECTROPHILIC ALKYLATIONS

The absolute stereochemistries of 8-OPP, 9-OPP, and 10-OPP obtained from incubation of bisubstrate analogs 1-OPP and 2-OPP with farnesyl-diphosphate synthase were determined by correlation of ORD spectra with those of synthetic materials. Only one enantiomer was found for each of the enzymatic products. The products from 1-OPP were (S)-8-OPP and (S)-10-OPP, while those from 2-OPP were (R)-8-OPP, (R)-9-OPP, and (R)-10-OPP. Conformational analysis of 1-OPP and 2-OPP, which considers topological limitations imposed by FPP synthase, indicates that the products from the enzymatic reactions are formed from discrete E.S complexes formed from different conformers of the substrates. Overlays of the conformations that give the observed products are consistent with a model where the hydrocarbon moieties occupy a central volume flanked on top and bottom by their diphosphate residues.