Studies of mammalian ornithine decarboxylase using a monoclonal antibody

A monoclonal antibody of the immunoglobulin M class was produced against mouse kidney ornithine decarboxylase. Screening for the antibody was carried out using alpha-difluoromethyl[5-3H]ornithine-labelled ornithine decarboxylase. The antibody reacted with this antigen and with native ornithine decarboxylase. The antibody attached to Sepharose could be used to form an immunoaffinity column that retained mammalian ornithine decarboxylase. The active enzyme could then be eluted in a highly purified form by 1.0M-sodium thiocyanate. The monoclonal antibody could also be used to precipitate labelled ornithine decarboxylase from homogenates of kidneys from androgen-treated mice given [35S]methionine. Only one band, corresponding to Mr of about 55000, was observed. The extensive labelling of this band is consistent with the rapid turnover of ornithine decarboxylase protein, since this enzyme represents only about 1 part in 10000 of the cytosolic protein.