Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzymes, Uncharacterized Proteins with similarity to Ornithine and Diaminopimelate Decarboxylases
This subfamily contains uncharacterized proteins with similarity to ornithine decarboxylase (ODC) and diaminopimelate decarboxylase (DapDC). ODC and DapDC 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. They exist as homodimers with active sites that lie at the interface between the TIM barrel domain of one subunit and the beta-sandwich domain of the other subunit. ODC participates in the formation of putrescine by catalyzing the decarboxylation of ornithine, the first step in polyamine biosynthesis. DapDC participates in the last step of lysine biosynthesis, the conversion of meso-2,6-diaminoheptanedioate to L-lysine. Proteins in this subfamily may function as PLP-dependent decarboxylases. Homodimer formation and the presence of the PLP cofactor may be required for catalytic activity.