STUDIES ON THE MUNG BEAN TRYPSIN INHIBITOR——REDUCTION AND REOXIDATION OF THE DISULFIDE BONDS OF THE LYS ACTIVE FRAGMENT

摘要

＜正＞ Two peptide chains A1 and A2 of the Lys active fragment, linked via a couple ofinter-disulfide bonds, could be separated from each other after reduction with dithiothreitoland gel filtration on Sephadex G-25. Reoxidation of the reduced peptide chain A1 resultedin recovering the inhibitory activity with 25% yield, based on the original activity of theLys fragment. The A1 active fragment was further purified by affinity chromatographywith immobilized trypsin. Sephadex G-25 gel filtration produced two forms of the A1 activefragment, the major fraction being a monomer and the minor one being a dimeer with loweractivity. The results obtained offered evidence of the evolution of mung bean inhibitorfrom an ancestral single-headed inhibitor by fused gene duplication with A2 as a connectingpeptide. The CD spectra of the Lys fragment and the reoxidized peptide chain A1 werealso compared.