The effect of ethylenedinitrilotetraacetic acid (EDTA) on the reaction between the guinea-pig C5 convertase and guinea-pig C5.
Guinea-pig C5 was reacted with EAC1423 in the washed-cell intermediate assay in the presence of glucose gelatin veronal buffer (GGVB), Zn2+-GGVB (0.025 mM), GGVB2+ containing Ca2+ and/or Mg2+ or EDTA (0.013 M)-GGVB. The EDTA inhibited the formation of competent SAC14235, while Ca2+ and/or Mg2+ had a slight enhancing effect compared to GGVB alone and Zn2+ gave a four-fold increase. Similar results were obtained by using human C5 with guinea-pig C5 convertase and functionally pure guinea-pig C6, C7, C8 and C9. When guinea-pig C6 was incorporated into these various reaction mixtures with guinea-pig C5, its addition markedly reduced the inhibition by EDTA, while Zn2+ still showed an enhancing effect. These results demonstrate that EDTA inhibited formation of competent SAC14235 by preventing activation of C5. The association of C6 with C5 can partially overcome the inhibition of C5 conversion by EDTA and may account for C5 activity in reaction mixtures containing C-EDTA.
D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D003166:Complement Activating Enzymes / Q000037:antagonists & inhibitors*; D050577:Complement C3-C5 Convertases; D003182:Complement C5 / Q000378:metabolism*; D003183:Complement C6 / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology*; D006168:Guinea Pigs; D006801:Humans; D007700:Kinetics; D015032:Zinc / Q000494:pharmacology
D002413:Cations, Divalent; D003182:Complement C5; D003183:Complement C6; D004492:Edetic Acid; D003166:Complement Activating Enzymes; D050577:Complement C3-C5 Convertases; D015032:Zinc