Abstract: Cathepsin B plays an important role in development and metabolism of insect.In present study,Cathepsin B（SCB）gene was cloned from Spodoptera frugiperda（J.E.Smmith）（GenBank accession number：HQ110064）.Bioinformatics analysis showed that the open reading frame（ORF）of SCB was 1 026 bp,encoding 341 amino acids,and the predicted N-terminus hydrophobic region contained 20 amino acid residues displaying the characteristic features of a signal peptide. The predicted molecular weight（MW）and isoelectric point（pI）of SCB was 35.6 kD and 6.59 respectively while excluding signal peptide. The similarity of Cathepsin B amino acid between S. frugiperda and other 15 species ranged from 51.2%-96.2%,while at the highest of 96.2% with Spodoptera exigua（Hiibner）.The three dimension structure of SCB was predicted by homology modeling method,SCB was found to fold into a tight global structure with the dynamic optimization and contain 6 disulfide bonds responsible for the stability of the structure,and hydrophilic amino acids were mainly coated on the surface of the protein. Moreover,molecular docking simulation showed that the SCB binding pocket was relatively shallow,wide and irregular. ARG19,VAL23,and ASN24 were the key amino acid residues at active sites of SCB,and the inhibitor CA-074me（CA）interacted strongly with these three key amino acid residues by mainly electrostatic interaction energy. CA formed 2 hydrogen bonds with VAL23 and ASN24 respectively. This study lays a foundation for the further research on structure and function of SCB by using biological experimental methods,and for the development of cathepsin inhibitor pesticides.

Key words: Sf9 cell, Cathepsin B, gene cloning, homology modeling, molecular docking, inhibitor