Other Notes Coenzymes and Cofactors, vol. 1: Vitamin B6, Pyridoxal Phosphate1,2 Application Pyridoxal 5-phosphate (PLP) (active form of Vitamin B6) is an enzyme prosthetic group that acts as a coenzyme in transamination, decarboxylation and deamination reactions such as the conversion of dopa into dopamine; of glutamate into GABA; of histidine to histamine. PLP works mechanistically through formation of a Schiff-base. |