Editing Pyridoxal phosphate (section)

==PLP-enzymes==
PLP is retained in the active site not only thanks to the lysine, but also thanks to the interaction of the phosphate group and a phosphate binding pocket and to a lesser extent thanks to base stacking of the pyridine ring with an overhanging aromatic residue, generally tyrosine (which may also partake in the acid–base catalysis). Despite the limited requirements for a PLP binding pocket, PLP enzymes belong to only five different families. These families do not correlate well with a particular type of reaction. The five families are classified as fold types followed by a Roman numeral.<ref name=rev/>
* Fold Type I   — aspartate aminotransferase family
* Fold Type II  — tryptophan synthase family
* Fold Type III — alanine racemase family (TIM-barrel)
* Fold Type IV  — D-amino acid aminotransferase family
* Fold Type V   — glycogen phosphorylase family