C3-convertase

C3-convertase (EC 3.4.21.43) is the name of the enzyme composed of the C4b-C2b complex, which forms during the Classical pathyway of the complement system.

It is formed when C1s cleaves off C2a from a membrane-bound C4b-C2 complex.

Once formed, C3-convertase will catalyze the proteolytic cleavage of C3 into C3a and C3b (hence the name "C3-convertase").