The isolation of the isopentenyl diphosphate (IPP) isomerase (EC 5.3.3.2) encoding gene(idi)ofPhaffia rhodozymaby a new and direct selection procedure in a carotenogenicEscherichia colistrain is described. Isopentenyl diphosphate (IPP) isomerase is a key enzyme in the isoprenoid biosynthetic pathway which catalyses the interconversion of the primary five—carbon diphosphate building blocks dimethylallyl diphosphate (DMAPP) and IPP. Our results imply that this method should be generally useful for the isolation of IPP isomerase encoding genes in both genomic and cDNA libraries from other organisms. The structural gene comprises 1294 nucleotides encoding a 28.7 kDa polypeptide of 251 amino acids. Analysis of the nucleotide and amino acid sequence indicates clear homology to IPP isomerases of non—carotenogenic yeasts,Schizosaccharomyces pombe(46%) andSaccharomyces cerevisiae(42%). By high level expression of the heterologous IPP isomerase gene in a recombinantE. colia3-fold increase in lycopene production was achieved. This indicates the potentials of thisidigene to improve carotenoid biosynthesis by metabolic pathway engineering in homologous and heterologous hosts.