Prenyltransferases catalyze the transfer of a prenyl group from one compound to another. They can be divided into 3 main classes: (i) isoprenyl pyrophosphate synthases, which catalyze chain elongation to generate linear isoprenyl pyrophosphates; (b) protein prenyltransferases, which catalyze the transfer of an isoprenyl pyrophosphate (e.g. farnesyl pyrophosphate) to a protein or a peptide; (c) terpenoid cyclases, which catalyze the cyclization of isoprenyl pyrophosphates. (Adapted from PMID:12135472).