title: Inhibition of the activation of the first component of complement, C1, by various amino acids or peptides.
abstract: The effects of various amino acids (or their analogues) and peptides on the activation or consumption of human complement by erythrocytes bound with hemolysin or heat-aggregated immunoglobulin G (aggIgG) were studied by using the hemolysis of hemolysin-bound erythrocytes, the consumption of complement by aggIgG in the serum, the hydrolysis of acetyl tyrosine ethyl ester by activated Cl (Cls), Cl hemolysis and a newly developed enzyme immunoassay, which directly measures interaction between Clq and aggIgG. Amino acids or peptides which were proposed to comprise Clq binding sites of the C2 region of IgG or their analogues were used. CH50 was inhibited by lysine or arginine to the largest extent, but other amino acids, including tranexamic acid and epsilon-amino caproic acid were not inhibitory up to 60 mM. The consumption of serum complement by aggIgG was prevented by arginine or lysine (about 60% inhibition at 60 mM) and by histidine to a lesser extent. The activation of Cls in the Cl complex by aggIgG precipitated at pH 5.5 was most inhibited by lysine, and to a lesser extent by tranexamic acid, arginine and epsilon-aminocaproic acid, but not glutamic acid or glycine. The results of Cl hemolysis indicated that, of all amino acids soluble at neutral pH, lysine and arginine were most effective in the inhibition of Cl hemolysis. Tranexamic acid and epsilon-aminocaproic acid were less effective, and glycine and norleucine were hardly effective. Among the dipeptides used, those that are composed of aromatic amino acids were very effective in the inhibition of Cl hemolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000596:Amino Acids / Q000494:pharmacology*; D003167:Complement Activation / Q000187:drug effects*; D003172:Complement C1 / Q000276:immunology*; D006461:Hemolysis / Q000187:drug effects; D006358:Hot Temperature; D006801:Humans; D006868:Hydrolysis; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000276:immunology; D066298:In Vitro Techniques; D010455:Peptides / Q000494:pharmacology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors
chemical_list: D000596:Amino Acids; D003172:Complement C1; D007074:Immunoglobulin G; D010455:Peptides; D014443:Tyrosine; C007651:ethyl N-alpha-acetyl-tyrosinate