Identical catalytic-centre activity for mouse kidney and rat liver ornithine decarboxylases as determined with antizyme and affinity labelling.

Since the catalytic-centre activity of mouse kidney ornithine decarboxylase (ODC) has been assumed to be twice as high as that of rat liver ODC, we compared relative catalytic-centre activity of the two enzymes by titration with antizyme, which inhibits ODC by stoichiometric binding. In either a crude or a purified state, both enzymes were inhibited by rat liver antizyme to the same extent, indicating that they have nearly identical catalytic-centre activities. This conclusion was supported by comparison of affinity labelling of the enzymes with alpha-difluoromethyl[14C]ornithine.