Studies on the environmental factors for the breeding of grain mites : VI. Digestive enzymes of the grain mites, Carpoglyphus lactis, Aleuroglyphus ovatus and Tyrophagus dimidiatus

Abstract

A series of experiments were made to see whether the differences in food habits by the species of the grain mites might be associated with the activities of some digestive enzymes. Three species of the grain mites, Carpoglyphus lactis, Aleuroglyphus ovatus and Tyrophagus dimidiatus, were collected from their cultures with the saturated saline floatation method, and were isolated and purified from their culture media by repeated applications of washing and centrifuging in saturated sodium chloride solution. The mite bodies were homogenized in 10 times of 15/M phosphate buffer (pH 7.0), centrifuged and the supernatants were tested for the activities of protease, esterase, amylase and saccharase. The protease activity as measured by Folin method was the highest at pH 7, 5 in Carpoglyphus and at 7.0 in Tyrophagus, while that in Aleuroglypus was the highest among the three species in strength and its optimum pH was at around 6. No significant differences were seen in esterase activities by the species. Amylase activity was the highest in Aleuroglphus, about twice as strong as the other two species, and its optimum pH was seen at 5.5 for all the species. Saccharase was the lowest in Aleuroglyphus and was about one fourth of the other two species, and its optimum pH was at about 5.0 for all the species tested.