Protein kinase catalysed phosphorylation of monoclonal and polyclonal immunoglobins

Radiolabelled tumour directed immunoglobulins have great potential as a means for both locating and treating solid tumours and their metastases. The radiochemical properties of ³²P make it a good candidate as a therapeutically useful isotope with which to tag immunoglobulins. We have tested the ability of cyclic AMP dependent protein kinase (cAMP dep PK), Casein Kinase II and Protein Kinase C to phosphorylate both a pan-reactive antiβ tubulin mouse monoclonal (IgG, type 2B, KMX-1) and a selection of polyclonal IgG fractions from different animals. None of the kinases were capable of inserting ³²P from [γ-³²P]ATP into the native immunoglobulins, but cAMP dep PK was found to be capable of phosphorylating all of the immunoglobulins tested after their partial denaturation in urea. This denaturation was found to be reversible. It was clear from our results that the domain into which ³²P is introduced varies markedly between immunoglobulins and we are now extending our studies to discover why this is the case.