3.4.21.43	complement component C2b accelerates dissociation	81406	
3.4.21.43	complex C4bC2a extremely unstable	81406, 81407	
3.4.21.43	decay-accelerating factor from guinea pig erythrocyte stroma accelerates decay	81410	
3.4.21.43	dilute iodine solution stabilizes	81406, 81414	
3.4.21.43	dissociation of the classical-complement-pathway C3/C5 convertase by the regulators decay-accelerating factor, DAF, complement receptor 1, CR1, factor H and C4-binding protein C4BP, controls the function of the enzyme. Decay acceleration mediated by DAF, C4BP and CR1 requires interaction of the alpha4/5 region of C2a with a CCO2/CCO3 site of DAF or structurally homologous sites of CR1 and C4BP	652494	
3.4.21.43	in the presence of C4b-binding protein C4BP the assembly of the classical pathway C3-convertase is prevented and its decay is accelerated. Positively charged amino acids at the interface between alpha-chain CCP1 and CCP2 of C4BP are required for regulation of the classical C3-convertase	653251	
3.4.21.43	the C3 convertase is stabilized by the binding of properdin	707849	
3.4.21.43	the enzyme has a very short half-life. Dissociation of the two noncovalently bound subunits proceeds with a half-life of 1-3 min at 37°C under physiological conditions, and this rate increases greatly if regulatory proteins are present. Numerous decay-accelerating proteins are present in plasma and on host cells that bind to the noncatalytic subunit C4b and increase the rate at which the catalytic subunit C2a is released into the medium. C2a loses its enzymatic activity and its ability to bind to C4b upon release. Although C4b is able to rebind C2 and reform the enzyme, the interaction with most decay-accelerating factors also leads to permanent proteolytic interaction of the cell-bound subunit C4b by a fluid-phase protease Factor I. Theses regulatory events limit cleavage of C3, reduce release of the anaphylatoxin C3a and control the formation of more efficient C5 convertase enzymes	649815