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. Author manuscript; available in PMC: 2010 Sep 1.
Published in final edited form as: Mol Immunol. 2009 Aug 5;46(15):2902–2910. doi: 10.1016/j.molimm.2009.07.006

Table 1.

Inhibition of formation of C3/C5 convertases by C4BP

Enzyme IC50a (nM)
Lectin pathway C3/C5 convertase
 Soluble C3 convertase (C4b,C2a) 1.05 ± 0.36
 Surface-bound C3 convertase (ZymM1,C4b,C2a) 1.27 ± 1.09
 Surface-bound C3 convertase (EManM1,C4b,C2a) 2.63 ± 1.69
 High Affinity C5 convertase (ZymM1,C3bC4b,C2a) 2.81 ± 2.46
 High Affinity C5 convertase (EManM1,C3bC4b,C2a) 42.66 ± 42.33
Classical pathway C3/C5 convertasesb
 Soluble C3 convertase (C4b,C2a) 5 ± 3
 Surface-bound C3 convertase (EAC1,C4b,C2a) 35 ± 12
 High affinity C5 convertase (EAC1,C3bC4b,C2a) 72 ± 16
a

IC50, C4BP concentration required to inhibit formation of C3 convertases and high affinity C5 convertases by 50% as described in Materials and Methods and shown in Figs. 1 and 2. The lectin pathway C3/C5 convertases were assembled on zymosan or EMan cells bearing different densities of C4b (21,000-346,000 C4b/Zym and 8,000-471,000 C4b/EMan). Values are mean ± S.D. (n = 3 or more)

b

IC50 values for classical pathway C3/C5 convertases that were assembled on EAC1 cells bearing different densities of C4b (9,300-462,000 C4b/EA) and have been reported previously (Rawal et al., 2007).