Genetic evidence of branching in the isoprenoid pathway for the productionof isopentenyl diphosphate and dimethylallyl diphosphate in Escherichia coli

An alternative mevalonate-independent pathway for isoprenoid biosynthesis h as been recently discovered in eubacteria (including Escherichia coli) and plant plastids, although it is not fully elucidated yet. In this work, E. c oli cells were engineered to utilize exogenously provided mevalonate and us ed to demonstrate by a genetic approach that branching of the endogenous pa thway results in separate synthesis of the isoprenoid building units isopen tenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). I n addition, the IPP isomerase encoded by the idi gene was shown to be funct ional in vivo and to represent the only possibility for interconverting IPP and DMAPP in this bacterium. (C) 2000 Federation of European Biochemical S ocieties.