Mouse Ornithine Decarboxylase: Structural Comparisons to Other PLP-Dependent Enzymes

Ornithine decarboxylases (ODCs) are PLP-dependent enzymes that initiate the first and rate-limiting step in the biosynthesis of polyamines. Sequence comparisons suggest four Groups of PLP-dependent decarboxylases, but there appear to be only two structural motifs. Decarboxylases of Groups I, II, and III possess a PLP-binding domain as seen in the structure of the bacterial ODC fromLactobacillus30a. The eukaryotic ODCs belong to the Group IV decarboxylases, which includes biosynthetic ArgDC and diaminopimelate DC. mODC is active as a dimer formed through a head-to-tail interaction between monomers. Each monomer contains two domains: an α/ β-barrel domain which binds the cofactor, and a second domain consisting mostly of β-structure. Analysis of the mODC active site provides insight into the stereochemical characteristics of PLP-dependent decarboxylation.