Complement factor 3 C3b C3(H2O):Factor Bb cleaves C3 to C3b and C3a Authored: de Bono, B, 2006-02-16 13:19:05 C3(H2O):Factor Bb is a C3 convertase, sometimes referred to as the initial C3 convertase (iC3). The Factor Bb component catalyzes the hydrolysis of C3 to produce C3b and C3a. This reaction is not known to be directly coupled to the association of C3b complexes with a cell surface. It is believed that a small proportion of C3b spontaneously associates with the cell surface, otherwise it is rapidly inactivated (Muller-Eberhard 1988). EC Number: 3.4.21 Edited: Jupe, S, 2010-11-17 Pubmed3052276 Reactome Database ID Release 43183130 Reactome, http://www.reactome.org ReactomeREACT_7948 Reviewed: D'Eustachio, P, 2006-07-03 21:35:13