PURIFICATION AND CHARACTERIZATION OF A GROUP OF 5 NOVEL PEPTIDE SERINE-PROTEASE INHIBITORS FROM OVARIES OF THE DESERT LOCUST, SCHISTOCERCA-GREGARIA

The ovary of the desert locust, Schistocerca gregaria, contains multip le inhibitors of serine proteases, Five serine protease inhibitors, de signated SGPI-1-5 (Schistocerca gregaria protease inhibitors) were pur ified from methanolic extracts of mature ovaries and analyzed by mass spectrometry and amino acid sequencing, The revealed primary structure s display amino acid similarities and are related to the serine protea se inhibitors identified in the hemolymph of Locusta migratoria. All i nhibitors show an in vitro inhibiting activity towards alpha-chymotryp sin. In addition, SGPI-1 displays in vitro inhibiting activity towards trypsin, and SGPI-2 is a potent pancreatic elastase inhibitor, Differ ences in inhibitory specificities towards the locust endogenous serine proteases can be readily attributed to the amino acid sequence within the active region and also to amino acid residues beyond the PI-P'1 b ond, A difference in one or two amino acid residues around the reactiv e sites results in considerable alteration of the inhibitor?, specific ity, The temporal and spatial distribution of SGPI-1-5 vl as studied b y RP-HPLC analysis, All inhibitors occur in hemolymph, ovaries, testes and fat body of adults but are absent in the gut. They are also prese nt in larval hemolymph and fat body, An antibody raised against SGPI-2 shows positive immunostaining in the ovarian follicle cells. (C) 1998 Federation of European Biochemical Societies.