C55-isoprenyl pyrophosphate

C55-isoprenyl pyrophosphate (also known as undecaprenyl pyrophosphate or C55-PP) is an essential molecule involved in the construction of the bacterial peptidoglycan cell wall. It is a receptor found in the plasma membrane of bacteria allowing glycan tetrapeptide monomers synthesized in the cell cytoplasm to translocate to the periplasmic space.

C55-P (undecaprenyl phosphate) is a related compound, containing one fewer phosphate group. It is produced from C55-PP by reaction EC 3.6.1.27, typically catalyzed by UppP/BacA. C55-P is recycled back into C55-PP later in the process. C55-OH is known as bactoprenol.