Dialkylglycine decarboxylase (DGD) is a pyridoxal 5-phosphate (PLP) dependent enzyme which catalyses the decarboxylation dependent transamination between dialkylglycine and pyruvate. The dialkylglycine is decarboxylated to give CO2 and a dialkylketone whilst the amino group is transferred to the PLP cofactor from where it reacts with pyruvate to produce L-alanine.
The resting state of most PLP dependent enzyme has the PLP linked covalently via a Schiff base to a lysine residue, referred to as the internal aldimime. The amino group of the substrate then reacts to replace the lysine, forming the external aldimime adduct. The PLP pyridoxal ring acts as an electron sink in the reaction.
DGD has been shown by structural analysis to be a member of the type I fold family. The central PLP domain of the subunits (most members are dimers or oligomers with dihedral symmetry, DGD is a tetramer) is an alpha/beta structure with a unique seven stranded beta sheet.
Defined by 6 residues: TRP:A-138GLU:A-210ASP:A-243GLN:A-246LYS:A-272ARG:A-406