Isopentenyl pyrophosphate (IPP) is an intermediate in the classical, HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids. IPP is formed from acetyl-CoA via mevalonic acid. IPP can then be isomerized to dimethylallyl pyrophosphate by the enzyme isopentenyl pyrophosphate isomerase.
IPP can be synthesized via the alternative, non-mevalonate pathway of isoprenoid biosynthesis instead, where it is formed from (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP) by the enzyme HMB-PP reductase (LytB, IspH). The non-mevalonate pathway is utilized by many bacteria, apicomplexan protozoa such as malaria parasites, and the plastids of higher plants.