C5-convertase

C5 convertase is an enzyme belonging to a family of serine proteases that play key role in the innate immunity. It participates in the complement cascade ending with cell death.

There are four different C5 convertases able to specifically convert C5 glycoprotein (α-, β-chain) to C5a and C5b fragments. Two of them are physiological complement enzymes, associate to the cell-surface and mediate the classical pathway (C4b2a3b) or the alternative pathway (C3bBbC3b) of complement cascade. Two fluid phase C5 convertases have been described: the classical pathway enzyme, C4b2aoxy3b and the cobra venom factor-dependent C5 convertase, CVFBb.