Purification of mouse brain ornithine decarboxylase reveals its presence as an inactive complex with antizyme

Mouse brain ornithine decarboxylase (ODC) was purified to near-homogeneity by using (NH4)2SO4 precipitation and chromatography on heparin-Sepharose, pyridoxamine phosphate-agarose and DEAE-cellulose. On SDS/polyacrylamide-gel electrophoresis, the final preparation gave one protein band similar to that obtained for purified mouse kidney enzyme, corresponding to an Mr of 53.000. The overall yield of the purification exceeded about 50-fold the total activity of the enzyme in the starting material. By affinity chromatography on ODC-bound Sepharose, the extra enzyme activity was shown to originate, at least partly, from the enzyme-antizyme complex. These results demonstrate that ODC in mouse brain occurs mainly in an inactive form and is activated during purification.