Cell surface:C4b:C2a Cell surface:C3b C4b:C2a:C3b Formation of classic C5 convertase Authored: de Bono, B, 2004-08-04 09:17:50 C5 convertases are serine proteases that cleave C5 with high efficiency; the C3 convertases can cleave C5 but have a poor affinity for C5, with a Km of 6-9 microM. The high affinity C5 convertases are generated when the low affinity C3/C5 convertases such as C4b:C2a deposit C3b by cleaving native C3. These C3b-containing C3/C5 convertases have Km values of 0.005 microM, well below the normal concentration of C5 in blood (0.37 microM). They have very low Vmax rates, just one C5 cleaved per 1–4 min per enzyme (Rawal & Pangburn 1998). Edited: Jupe, S, 2010-11-17 Pubmed12878586 Pubmed9642242 Reactome Database ID Release 43173636 Reactome, http://www.reactome.org ReactomeREACT_8022 Reviewed: D'Eustachio, P, 2006-07-03 21:35:13