PROTEASE-LIKE ACTIVITIES IN PLASMA OF DIFFERENT ANIMALS

Hydrolysis of chromogenic p-nitroanilide substrates by plasma samples revealed that guinea-pig and rat showed high kallikrein and thrombin a ctivities followed by mouse and man. The relative rate of hydrolysis o f S-2302[H-D-Pro-Phe-Arg p-nitroanilide, substrate for plasma kallikre in] and S-2238[H-D-Phe-Pip-Arg p-nitroanilide, substrate for thrombin] were as follows : Guinea-pig [96.4, 29.0 units/ml], rat [78.8. 21.0], mouse [23.2. 10.2] and man [15.0. 14.0]. Other species showed much lo wer levels. Trypsin and elastase activities were low in all the eight species studied. Rat and human kallikreins were inhibited by soya bean trypsin inhibitor hut not by Lima bean inhibitor, Rat and mouse plasm a samples also showed high chymotrypsin-like activity as evidenced by hydrolysis of acetyl tyrosine ethyl ester(107 and 125 units/ml respect ively). However, action on S-2586 (carbomethoxy propionyl-Arg-Pro-Tyr p-nitroanilide, another chymotrypsin substrate) was poor both with rat and mouse. Acetyl tyrosine ethyl ester hydrolytic activity in rat pla sma was sensitive to phenylmethyl sulfonyl fluoride and tosyl phenylal anine chloromethyl ketone but not to high molecular weight plant prote ase inhibitors.