Purification and characterization of proteinase inhibitor from Artocarpus integrifolia seeds

Abstract

A trypsin-chymotrypsin inhibitor has been isolated and purified from seeds of the jackfruit plant, Artocarpus integrifolia. Its purity has been checked by PAGE, isoelectric focusing, immunochemical tests and sedimentation in the ultracentrifuge. The inhibitor has an M_r of 44 200 and a pI of 4.5. It consists of two disulphide-linked polypeptide chains having M_rs of 24 700 and 18 600. Amino acid analyses have shown that it contains three half-cystine residues and is rich in aspartic acid, glutamic acid and leucine. It contains 3% neutral sugar and 1.8% glucosamine. It inhibits trypsin and chymotrypsin at independent reactive sites by forming enzyme-inhibitor complexes at a molar ratio close to unity. Chemical modification of amino groups with trinitrobenzene sulphonic acid has reduced its inhibitory activity against trypsin with no loss of chymotrypsin inhibitory activity.