INHIBITION OF CLASSICAL AND ALTERNATIVE PATHWAYS BY AMINO-ACIDS AND THEIR DERIVATIVES

Abstract

Effects of various amino acids and their derivatives on the classical pathway and alternative pathway of [human and guinea pig] complement [C] were studied. Leupeptin, acetyl-leucyl-leucyl-arginal, inhibited CH50 [total hemolytic C] and C1-esterase, but did not inhibit the alternative pathway. When amino acids of carbon chains of the order of 7 were used, arginine and lysine had stronger effects than trans-aminomethyl cyclohexane carboxylic acid (t-AMCHA), cis-aminomethyl cyclohexane carboxylic acid (cis-AMCHA) and .epsilon.-aminocaproic acid (EACA). SH-compounds, cysteine, homocysteine and glutathione had the strongest inhibitory effects among these amino acids on classical and alternative pathways. When effects on C1 esterase were compared, arginine, lysine, t-AMCHA, cis-AMCHA and EACA had weak inhibition; SH-compounds showed strong inhibition. Poly-L-lysine, which had extremely strong inhibition of CH50, had no inhibition on C1 esterase. The inhibitory effects of antifibrinolytic agents, EACA and t-AMCHA, were weak, but when effects on early parts of the classical pathway C(1,4,2)H50 were tested, some inhibitory activities were recognized. Inhibitory effects of these agents were due to their activities on the early parts of the classical pathway.