Chinese hamster ovary cells resistant to alpha-difluoromethylornithine are overproducers of ornithine decarboxylase.

The selection of Chinese hamster ovary cells resistant to ornithine analogues has been extended to very high levels of the suicide inhibitor alpha-difluoromethylornithine. Stepwise selections resulted in stepwise increases in the inducible levels of ornithine decarboxylase activity. The enzyme is shown by several criteria to be normal in every respect: regulation in the cell cycle, inhibition by antizyme, absolute specific activity as determined with the help of alpha-[3H]difluoromethylornithine. The enzyme has been highly purified from such overproducing cells. The subunit molecular weight of the mammalian enzyme has been confirmed to be approximately 54,000. The location of the enzyme in two-dimensional polyacrylamide gel electrophoresis was determined, and the protein could be detected on two-dimensional gels with extracts from our best overproducers.