3.4.21.47	factor B	generation of the AP C3-convertase initiates by the binding of factor B to C3b to form the proconvertase, C3bB. Factor B undergoes a dramatic conformational change upon binding to C3b, it binds near the C345C domain in C3b. Factor B-D279G mutant promotes high-affinity C3b-binding and is correctly cleaved by factor D in the C3bB proenzyme to generate a very stable, functionally-active, AP C3-convertase C3bBb	701017	
3.4.21.47	factor B	the classical C5 convertase requires factor D and factor B for activation and complex assembly	732705	
3.4.21.47	factor C	acts as an LPS-responsive C3 convertase on the surface of invading Gram-negative bacteria in the initial phase of horseshoe crab complement activation. The proteolytic activity of factor C on the surface of Escherichia coli is essential for the deposition of C3b	699342	
3.4.21.47	factor D	the classical C5 convertase requires factor D and factor B for activation and complex assembly	732705	
3.4.21.47	factor D	the proconvertase C3bB is cleaved by factor D at a single site in factor B, producing Ba and Bb fragments. Ba dissociates from the complex, while Bb remains bound to C3b, forming the active AP C3-convertase C3bBb	701017	
3.4.21.47	formyl-methionyl-leucylphenylalanine	treatment of whole blood leads to stimulation of neutrophils resulting in activation of the alternative complement pathway and release of C5 fragments, which further amplify proinflammatory responses	717421	
3.4.21.47	human complement factor H-related protein 4	CFHR 4, two isozymes A and B of 86 and 45 kDa from plasma, domain structure, overview. The protein belongs to the factor H family of plasma glycoproteins that are composed of short consensus repeat (SCR) domains. It activates complement by serving as a platform for the assembly of alternative pathway C3 convertase via its interaction with C3b protein. CFHR4 binds C3b via its C-terminus, and it lacks SCRs homologous to the complement inhibitory domains of factor H and has no significant complement regulatory activities. In contrast to the complement inhibitor factor H, CFHR4 acts as an enhancer of opsonization by promoting complement activation	732056	
3.4.21.47	LPS	proteolytic conversion of C3 to C3b in hemocyanin-depleted plasma is strongly induced by LPS	699342	
3.4.21.47	mannan-binding lectin	binding to O antigen-specific oligosaccharides derived from Salmonella sp. corresponding to serogroup C, and efficient support of component C3 deposition in the absence of C2, C4, or the associated serine protease 2	669628	
3.4.21.47	mannan-binding lectin	mannan-binding lectin (MBL) promotes activation of complement component C3 through the combined action of MBL-associated serine proteases MASP-1 and MASP-2 without appreciable involvement of the alternative pathway	680169