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 2.6. Retains 95% and 79% of the original activity after incubation for 30 days at pH 3.0 and pH 10.0 respectively. Optimum temperature is 55 degrees Celsius. Thermostable up to 50 degrees Celsius. Retains 60% of the original activity after incubation for 30 days at 50 degrees Celsius. Belongs to the peptidase A1 family.