REGULATION OF THE ESCHERICHIA-COLI BIOSYNTHETIC ORNITHINE DECARBOXYLASE ACTIVITY BY PHOSPHORYLATION AND NUCLEOTIDES

A protein kinase which phosphorylates in vitro the biosynthetic ornith ine decarboxylase (ODC) was partially purified from Escherichia coli. In vivo phosphorylation of ODC occurs after incubation of E. coli with [P-32]orthophosphate. When the recombinant ODC was incubated sith cal f intestine alkaline phosphatase it was inactivated and this inactive ODC could be reversibly activated allosterically only by guanyl or ura cyl phosphate analogues at a concentration of 10(-4) or 10(-3) M. The pH optimum of the [8-H-3]GTP binding was determined and it was shown t hat the GTP binding is proportional to the amount of ODC. The [8-H-3]G TP binds specifically to ODC as was proved by the addition af cold GTP or ATP. High concentration of GTP can dissociate the ODC-antizyme com plex and either reactivate or liberate the ODC. Therefore, a working h ypothesis is suggested describing the regulation of ODC by phosphoryla tion-dephosphorylation reaction dr by antizyme and nucleotide analogue s interaction.