Properties of protease inhibitors from the haemolymph of silkworms, Bombyx mori, Antheraea pernyi and Philosamia cynthia ricini.

1. Effects of inhibitors in the haemolymph from three silkworms on proteases from the alimentary canal of respective insects were studied as well as those on bovine trypsin and alpha-chymotrypsin. 2. In Bombyx haemolymph, three inhibitor fractions were separated by gel filtration on Sephadex G-75. These fractions differed in the specificity of inhibition for different proteases and in thermal stability. 3. In Antheraea haemolymph, a relatively different elution profile was observed compared to that of Bombyx. Philosamia haemolymph showed the intermediate type of elution pattern. 4. Inhibitors from the haemolymph of Antheraea and Philosamia were heat stable. 5. Distinct electrophoretic patterns of inhibitors were observed in three silkworms.