Extracellular proteinase found in the pitcher fluid of carnivorous plants. Digest prey for nitrogen uptake. Similar to pepsin, but also cleaves on either side of Asp and at Lys-|-Arg. Inhibited by pepstatin and by diazoacetyl-D,L-norleucine methyl ester (DAN) in the presence of Cu(2+) ions. Optimum pH is 3.0. Retains 80% and 60% of the original activity after incubation for 30 days at pH 3.0 and pH 4.0 respectively. Unstable at pH higher than 5.0. Optimum temperature is 45 degrees Celsius. Thermostable up to 50 degrees Celsius. Retains 44% of the original activity after incubation for 30 days at 50 degrees Celsius. Belongs to the peptidase A1 family.