presqualene pyrophosphate

Presqualene pyrophosphate is an intermediate compound in the biosynthesis of isoprenoids. Isoprenoids are a large and diverse class of organic molecules that are built from five-carbon units derived from isoprene. These compounds are found throughout nature and include molecules like carotenoids and terpenes.

The biosynthesis of isoprenoids typically involves the head-to-tail coupling of isoprene units. However, some larger isoprenoids, such as squalene, are formed through a tail-to-tail coupling of smaller isoprenoid precursors. Presqualene pyrophosphate is a key intermediate in this tail-to-tail coupling process, formed when a necessary reductant is omitted during squalene synthesis. Its accumulation and subsequent conversion to squalene were elucidated by chemists like John Cornforth.1