Fluid phase destruction of C2hu by C1hu. I. Its enhancement and inhibition by homologous and heterologous C4.
The fluid phase inactivation of C2(hu) by C1(hu) is markedly enhanced by the presence of C4(hu). The enhancement is afforded by C1 inactivated C4(hu), namely C4i(hu), and requires the simultaneous presence of enzymatically active C1. Heterologous C4 of guinea pig origin protects C2(hu) from the inactivation by C1(hu). Thus, in both the fluid phase and on the cellular intermediate, C4(hu) is essential to the specific action of C1(hu) on C2(hu). It is possible that C4i alters C2 so as to present a more suitable substrate to the C1 enzyme or that C4i acts on the C1 to uncover a specificity for native C2.
D000818:Animals; D001665:Binding Sites; D003165:Complement System Proteins / Q000302:isolation & purification; D006168:Guinea Pigs; D006461:Hemolysis; D006801:Humans; D007700:Kinetics
D003165:Complement System Proteins