Digestive glucosidases in the midgut of Apodiphus amygdali Germar (Hemiptera: Pentatomidae)

Abstract

Apodiphus amygdali or stink bug of fruit trees is one of the polyphagous species from pentatomid bugs that attack many of fruit trees and ornamental trees. In the current study, activities of α- and β-glucosidases were measured in the midgut of A. amygdali adults. It was found the higher activity of β-glucosidase than α-glucosidase in addition to different enzymatic properties of the enzymes. Optimal pHs for enzymatic activities were found to be 5 and 7 for α- and β-glucosidases, respectively. Values regarding optimal temperatures were obtained at 30 °C for both α- and β-glucosidases. Among ions used on α-glucosidase activity, K+ and Ca2+ significantly increased enzymatic activity, Na+ had no effect, and Cu2+, Fe2+ and Mg2+ had the significant negative effects on the enzyme activity. Ca2+ and Fe2+ increased β-glucosidase activity in the midgut of A. amygdali, Na+ had no effect, and other ions significantly decreased the enzyme activity. Ethylene glycol-bis (β-aminoethylether) N,N,N−,N-tetraacetic acid (EGTA), citric acid, ethylenediamide tetraacetic acid (EDTA) and sodium dodecylsulfate (SDS) significantly decreased α-glucosidase activity but EGTA, triethylenetetramine hexaacetic acid (TTHA), EDTA and SDS decreased β-glucosidase activity in the midgut of A. amygdali. Characterisation of digestive enzymes, especially the effect of inhibitors on enzyme activity, could be useful for better understanding of enzyme roles in nutritional physiology of insects in addition to reach safe and useful controls of insect pests.