COMPLEMENT AS A MEDIATOR OF INFLAMMATION. ENHANCEMENT OF VASCULAR PERMEABILITY BY PURIFIED HUMAN C'1 ESTERASE.

Purified preparations of the esterase derived from the first component of complement (C'1 esterase) increased vascular permeability in guinea pig skin, an effect inhibited by triprolidine, an antihistaminic agent, but not by soy bean trypsin inhibitor. The permeability-increasing and esterolytic properties of C'1 esterase were inhibited in parallel by the serum inhibitor of C'1 esterase, diisopropylphosphofluoridate and extremes of temperature and pH. Moreover, the permeability-increasing and esterolytic properties evolved in parallel when C'1 esterase was generated from its subcomponents.

The enhancement of chloroform-induced plasma proteolytic activity by epsilon aminocaproic acid.

The proteolytic activity in chloroform-treated plasma euglobulins has been attributed to plasmin. Plasmin can digest both casein and fibrin. Epsilon aminocaproic acid, which inhibits the activation of plasminogen, the precursor of plasmin, by streptokinase, urokinase, and tissue activators enhanced the development of casein hydrolytic activity in a mixture of chloroform and plasma euglobulins.

Studies on the activation of a proesterase associated with partially purified first component of human complement.

It has been found that under a wide range of physico-chemical conditions a positive correlation exists between the rate of disappearance of hemolytically active, partially purified first component of human complement and the rate of activation of an esterase hydrolyzing N-acetyl-L-tyrosine ethyl ester. Both reactions follow the kinetic equation for second order autocatalysis, with an apparent energy of activation of 31,000 calories per mol. They occur optimally at pH 7.

Some properties of an esterase derived from preparations of the first component of complement.

Studies on an esterase derived from partially purified preparations of the first component of complement are described. The esterase hydrolyzed certain synthetic amino acid esters, among which N-acetyl-L-tyrosine ethyl ester was most susceptible. This was hydrolyzed maximally between pH 7.