A variety of isoprenoid compounds are synthesized by various organisms. Forexample in eukaryotes the isoprenoid biosynthetic pathway is responsible forthe synthesis of a variety of end products including cholesterol, dolichol,ubiquinone or coenzyme Q. In bacteria this pathway leads to the synthesis ofisopentenyl tRNA, isoprenoid quinones, and sugar carrier lipids. Among theenzymes that participate in that pathway, are a number of polyprenylsynthetase enzymes which catalyze a 1'4-condensation between 5 carbon isopreneunits.It has been shown [<cite idref="PUB00002569"/>, <cite idref="PUB00002344"/>, <cite idref="PUB00002687"/>, <cite idref="PUB00004527"/>, <cite idref="PUB00004795"/>] that all the above enzymes share some regions ofsequence similarity. Two of these regions are rich in aspartic-acid residuesand could be involved in the catalytic mechanism and/or the binding of thesubstrates. Polyprenyl synthetase