Trypsin and aminopeptidase gene expression is affected by age and food composition in Anopheles gambiae

The effects of age and food composition on the expression of trypsin and aminopeptidase genes in the Anopheles gambiae gut were investigated. No trypsin mRNA was detected in the gut of newly eclosed females, but this mRNA accumulated to relatively high levels within the first day of life. In contrast, low, but significant trypsin enzyme activity was observed in newly eclosed females. Subcellular fractionation experiments suggested that abdominal distention induces the secretion of the enzyme into the lumen. Blood, but not a protein-free meal, induced the accumulation of new trypsin mRNA and enzyme. Unlike trypsin, substantial aminopeptidase activity was detected in newly eclosed and in older, sugar fed mosquitoes. Moreover, the subcellular localization of aminopeptidase did not change appreciably with hind ingestion, and the early increase of enzyme activity was independent of food composition.