Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzyme Arginine Decarboxylase
This subfamily includes plants and biosynthetic prokaryotic arginine decarboxylases (ADC, EC 184.108.40.206). ADC is involved in the biosynthesis of putrescine, which is the precursor of aliphatic polyamines in many organisms. It catalyzes the decarboxylation of L-arginine to agmatine, which is then hydrolyzed to putrescine by agmatinase. ADC is homologous to eukaryotic ornithine decarboxylase (ODC) and diaminopimelate decarboxylase (DapDC), which are fold type III PLP-dependent enzymes that contain an N-terminal PLP-binding TIM-barrel domain and a C-terminal beta-sandwich domain, similar to bacterial alanine racemases. Homodimer formation and the presence of both PLP and Mg2+ cofactors may be required for catalytic activity. Prokaryotic ADCs (biodegradative), which are fold type I PLP-dependent enzymes, are not included in this family.