摘要
The Lys active fragment of the mung bean trypsin inhibitor is composed of two peptidechains,one with 26 amino acid residues and the other with 9 residues linked by two interdisulfide bonds.The two peptide chains could be separated successfully from each other by reduction.with DTT followedby gel filtration.The reduced long peptide chain containing 6 Cys residues was subjected to air oxidation,and about 25% of the original antitrypsin activity of the Lys fragment was recovered.Following the previ-ously reported sequence,the solid-phase synthesis of this long peptide chain and its disulfide bond refold-ing are presented.Unexpectedly,the synthetic peptide showed much lower antitrypsin activity than thenatural one after reduction and air reoxidation.In order to explain this uncompatible result,we redeter-mined the sequence of the native long peptide chain of the Lys active fragment and obtained the result thatthe P′<sub>2</sub> position is Ile instead of Lys as previously reported.To ascertain the correct sequence,we synthe-sized another 22-peptide following the newly determined 26-peptide sequence,and skimming two residuesrespectively from N-terminus and C-terminus.After reduction and reoxidation,the synthetic 22-peptidehad the same antitrypsin activity as that of the native 26-peptide.Meanwhile,an analogue of this 22-pep-tide in which the residue Lys at the reactive site was replaced by Ala was also synthesized.This syntheticanalogue did not show any activity either to trypsin or to elastase.
The Lys active fragment of the mung bean trypsin inhibitor is composed of two peptide chains,one with 26 amino acid residues and the other with 9 residues linked by two interdisulfide bonds. The two peptide chains could be separated successfully from each other by reduction.with DTT followed by gel filtration.The reduced long peptide chain containing 6 Cys residues was subjected to air oxidation, and about 25% of the original antitrypsin activity of the Lys fragment was recovered.Following the previ- ously reported sequence,the solid-phase synthesis of this long peptide chain and its disulfide bond refold- ing are presented.Unexpectedly,the synthetic peptide showed much lower antitrypsin activity than the natural one after reduction and air reoxidation.In order to explain this uncompatible result,we redeter- mined the sequence of the native long peptide chain of the Lys active fragment and obtained the result that the P′_2 position is Ile instead of Lys as previously reported.To ascertain the correct sequence,we synthe- sized another 22-peptide following the newly determined 26-peptide sequence,and skimming two residues respectively from N-terminus and C-terminus.After reduction and reoxidation,the synthetic 22-peptide had the same antitrypsin activity as that of the native 26-peptide.Meanwhile,an analogue of this 22-pep- tide in which the residue Lys at the reactive site was replaced by Ala was also synthesized.This synthetic analogue did not show any activity either to trypsin or to elastase.
