Constitutive trypsin that is expressed 2 days after emergence, coinciding with host seeking behavior of the female. Preferential cleavage: Arg-|-Xaa, Lys-|-Xaa. Expressed in the midgut. Expression levels drop a few hours after blood feeding and pick up again 28 hours later. Belongs to the peptidase S1 family. As this protein has Gly-222 in the position that determines the specificity of the enzyme instead of the Asp found in trypsins, it could have a chymotrypsin-like activity.