Pyridoxal phosphate (PLP, pyridoxal 5'-phosphate, P5P) is a coenzyme, the active form of vitamin B6. Pyridoxal 5′-phosphate (PLP) is used as a cofactor for a wide range of enzymes including mitochondrial cysteine desulfurase, cystathionine γ-synthase (CGS), ornithine 4,5-aminomutase (OAM), and d-serine dehydratase. The versatility of PLP arises from its ability to covalently bind the substrate, and then to act as an electrophilic catalyst, thereby stabilizing different types of carbanionic reaction intermediates. PLP acts as a coenzyme in all transamination reactions, in various beta-elimination reactions, in the condensation reaction in heme synthesis.

Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3'-5'-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP) by adenylate cyclase located on the inner side of the plasma membrane and anchored at various locations in the interior of the cell. Around 1960 Earl W. Sutherland, Jr. showed that cyclic adenosine monophosphate (cAMP) serves as the secondary messenger within the cell. Cyclic AMP works by activating protein kinase A (PKA, or cAMP-dependent protein kinase). PKA is normally inactive as a tetrameric holoenzyme, consisting of two catalytic and two regulatory units with the regulatory units blocking the catalytic centers of the catalytic units. Cyclic AMP binds to specific locations on the regulatory units of the protein kinase, and causes dissociation between the regulatory and catalytic subunits, thus enabling those catalytic units to phosphorylate substrate proteins. It was discovered, that melanocytes require the RAS/RAF/MEK/ERK and the cyclic AMP (cAMP) signaling pathways to maintain the fine balance between proliferation and differentiation. cAMP suppressed CRAF activity in melanocytes and that was essential to suppress the oncogenic potential of CRAF in the cells. When RAS was mutated in melanoma, the cells switched their signaling from BRAF to CRAF. That switch was accompanied by dysregulated cAMP signaling, a step that was necessary to allow CRAF to signal to MEK. Thus, a fundamental switch in RAF isoform usage occurs when RAS was mutated in melanoma, and that occurs in the context of disrupted cAMP signaling. These data have important implications for the development of therapeutic strategies to treat this life-threatening disease.