Comparison of inhibition of the action of C1 on C4 by two synthetic substrates of C1 esterase, TAMe and ATEe

Two synthetic substrates, TAMe and ATEe, were tested for their abilities to inhibit the formation of SAC14 and SAC142 and found to act as inhibitors in different ways. In addition to inhibition of the formation of SAC142 from SAC14 and C2, TAMe inhibited the formation of SAC14 from SAC1 and C4 and the inactivation of C4 by C1 and EAC1. ATEe inhibited the formation of SAC14, but only slightly inhibited the inactivation of C4 by C1 and EAC1 and further did not interfere with the formation of SAC142. ATEe could be entirely replaced by acetyl-L-tyrosine in these effects on the action of C1 on C4. The possible mechanism of inhibitions by these compounds was discussed.