Effects of two proteinase inhibitors on the digestive enzymes and survival of honey bees ( Apis mellifera)

Abstract

Two endopeptidase inhibitors, BPTI (bovine pancreatic trypsin inhibitor) and SBTI (Kunitz soybean trypsin inhibitor), were found to significantly reduce the longevity of adult honey bees ( Apis mellifera L.) fed the inhibitors ad lib in sugar syrup at 1.0%, 0.5% or 0.1%, but not at 0.01% or 0.001% (w:v). Bees were taken from frames at emergence, kept in cages at 33 °C, and provided with a pollen/protein diet, water and syrup. In vivo activity levels of three midgut endopeptidases (trypsin, chymotrypsin and elastase) and the exopeptidase leucine aminopeptidase (LAP) were determined in bees fed either BPTI or SBTI at 1.0%, 0.3% or 0.1% (w:v) at two time points: the 8th day after emergence and when 75% of bees had died. LAP activity levels increased significantly in bees fed with either inhibitor at all concentrations. At day 8, bees fed BPTI at all concentrations had significantly reduced levels of trypsin, chymotrypsin and elastase. At the time of 75% mortality, bees fed BPTI at each concentration had reduced trypsin levels, but only those fed the inhibitor at the highest dose level had reduced chymotrypsin or elastase activity. At both time points, only bees fed SBTI at the highest concentration had lowered trypsin, chymotrypsin and elastase activities.