Effects on human group X phospholipase A2 inclusion bodies folding

Human group X phospholipase A(2) is a member of mammalian secretory phospholipase which belongs to phospholipase A(2) superfamily. It has been expressed in a form of inclusion bodies in E.coli. It could not retold efficiently as human pancreatic phospholipase A(2) (group I B) merely by diluting the protein unfolded in 8 mol/L of urea. The refolding reaction of human group X phospholipase A(2) in vitro was depended on temperature, pH and protein concentration. A number of additives have been tested, among which L-arginine was the most efficient effector in improving the refolding of human group X phospholipase A(2), and its structural analogs, L-citrulline, had less effect. L-lysine and L-arginine methyl ester could not improve phospholipase A(2) refolding. In addition, L-arginine inhibited the formation of aggregates and of intramolecular disulfide bonds. These results showed that both carboxyl and guanidyl residues of L-arginine were essential for improving protein refolding.