Abstract: 【Aim】 This study aims to explore the composition of amino acid residues in the active site of soluble trehalase from Helicoverpa armigera by analyzing the effect of chemical modification on this enzyme activity. 【Methods】 Chemical modification method was used to investigate the effect of chemical modifier on the soluble trehalase activity in the 5th instar larvae of H. armigera. The number of amino acid residues in active center was obtained from the deactivation rate constant of the modification reaction. 【Results】 The soluble trehalase activity in the 5th instar larvae of H. armigera was reduced by 81.58% and 54.14% after chemical modification by 8 mmol/L carbodiimide (EDC) and 25 mmol/L phenylglyoxal (PG), respectively, indicating that the modification of carboxylic acid group and arginine residues can inhibit the soluble trehalase activity effectively. The treatment with the substrate trehalose prevented the loss of enzyme activity from the chemical modification. Kinetic studies on chemical modification showed that the active site of soluble trehalase includes one carboxylic acid group and two arginine residues. 【Conclusion】 These results indicate that two carboxylic amino acids, i.e., glutamic acid and aspartic acid, are the vital residues of the active site of the soluble trehalase, and arginine is essential for the trehalase activity. These results provide theoretical support for the development of new pesticides.

Key words: Helicoverpa armigera; trehalase, chemical modification, active site, deactivation rate constant