Pyridoxal 5'-phosphate 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. Pyridoxal 5'-phosphate is used in the studies of PLP-dependent enzyme active sites.