Comparison of the activities of wild type and mutant enhancing factor/mouse secretory phospholipase A2 proteins

Enhancing factor (EF) protein, an isoform of secretory phospholipase A₂ (PLA₂), was purified as a modulator of epidermal growth factor from the small intestine of the Balb/c mouse. It was for the first time that a growth modulatory property of sPLA₂ was demonstrated. Deletion mutation analysis of EF cDNA carried out in our laboratory showed that enhancing activity and phospholipase activity are two separate activities that reside in the same molecule. In order to study the specific amino acids involved in each of these activities, two site-directed mutants of EF were made and expressedin vitro. Comparison of enhancing activity as well as phospholipase A₂ activity of these mutant proteins with that of wild type protein helped in identification of some of the residues important for both the activities.