Characteristics Of Trehalase And Inhibitory Effect Of Eight Insecticides On Its Activity In Plutella Xylostella

Trehalase is the only enzyme which hydrolyze trehalose of insects. When trehalose is transported to various tissues through haemolymph, it can be hydrolyzed by trehalase into glucose and utilized by cells. In view of the fact that trehalase plays an important role in energy metabolism of insects, many chemists are devoted to the research of new pecticide, which inhibited the activity of trehalase, disorder energy metabolism, achieving the purpose of the insect disinfestation. There have been many reports about trehalases,but trehalase of Plutella xylostella have not been studied. The characteristics of trehalase and the effects of effectors on its activity of Plutella xylostella were studied. The results were showed as follows:1. The trehalase of Plutella xylostella indicated that the optimum pH value of trehalase was6.0and the enzyme had a stable activity between5.0～6.0; The optimum temperature was50℃, and the enzyme had a stable activity between45℃～55℃; The Michaelis constant (Km) of trehalase hydrolyzing trehalose was (12.57±0.99)mmol/L. The maximum velocities (VmaX) hydrolyzing trehalose was (0.775±0.04)mmol/(min·g pro).2. The effects of diffenent organic solvents on the trehalase activity were compared. The results showed that carbinol, propanol and dioxane activate the enzyme activity; Glycerol could promote the enzymic activity at the low concentration but show inhibitory effect on trehalase activity at the high concectration; Acetaldehyde and glutaraldehyde have inhibitory effects on the enzyme activity, but acetone and DMSO had no obvious effect on enzymic activity.3. The effects of diffenent metal ions on the trehalase activity ere compared. The result showed that Na+could increase the activity of enzyme, while Cu2+, Ca2+, Fe3+and Al3+decrease the activity in varying degrees, and li+, Hg+and Mg2+had no obvious effect on enzymic activity. Zn2+could promote the enzyme activity at the low concentration but show inhibitory effect With the increase of concentration.4. At the40mg/L of insecticides (profenofos, indoxacarb, methomyl, fenobucarb, spinosad, dinotefuran, thiamethoxam and imidacloprid), there are different inhibitory effects on trehalase in4th instar larvas of plutella xylostella, their percentages of inhibition to trehalase activity were25.83%,20.59%,20.19%,18.99%,18.62%,15.15%,14.07%and13.53%respectively. Their inhibitory effects on trehalase activity were enhanced with the increasing of insecticide concentrations.