Interaction of C1s and C1 inactivator in the presence of heparin, dextran sulfate and protamine sulfate

When Cls? was mixed with Cl inactivator (ClINA) and the mixture was added with ATEe (acetyl tyrosine ethyl ester), the hydrolysis of ATEe decreased. The addition of heparin or dextran sulfate resulted in more hydrolysis of ATEe by the mixture of Cls? and ClINA, thus indicating the inhibition of ClINA activity. When the mixture of Cls? and ClINA was added to S-2238 (H-D-Phe-Pip-Arg-pNA), the hydrolysis of S-2238 by the mixture was the same as its hydrolysis by Cls? alone, thus ClINA being unable to inhibit Cls?'s capacity to hydrolyze S-2238. The addition of heparin did not affect the extent of hydrolysis of S-2238 by the mixture of Cls? and ClINA. When protamine sulfate was added to Cls?, Cls? activity was inhibited, but the addition of ClINA to the mixture of Cls? and protamine sulfate resulted in the same extent of inhibition of Cls? as the inhibition of Cls? by ClINA in the absence of protamine sulfate. It may be possible that Cls? has two sites, one interacting with both ClINA and protamine sulfate, the other being responsible for hydrolysis of S-2238 which is not inhibited by ClINA. As to influences of polycations and anions on hemolytic activities of the complement system, polyanions inhibited both the classical and alternative pathways to the same extent, but polycations primarily inhibited the classical pathway, and the extent of the inhibition of the alternative pathway by polycation was small.