Complement C3 (C3) is the most abundant component of the complement system, with levels in human plasma of ~1.2-1.5 mg/ml. It is central to the activation of both the classical and alternative complement pathways, both of which lead to the proteolytic processing of C3 to C3a and C3b. C3 exists as a heterodimer with molecular masses of 115 kDa and 75 kDa, although it is readily processed to create C3a, C3b or C3c depending on the processed state. MW: 138 kDa. Purity ≥95%