ID 3.4.21.47 DE alternative-complement-pathway C3/C5 convertase. AN C3 convertase. AN C3 proactivator. AN C5 convertase. AN complement component C3/C5 convertase (alternative). AN complement factor B. AN properdin factor B. CA Cleavage of Arg-|-Ser bond in complement component C3 alpha-chain to CA yield C3a and C3b, and Arg-|-Xaa bond in complement component C5 alpha- CA chain to yield C5a and C5b. CC -!- A bimolecular complex of complement fragment Bb with either C3b or CC cobra venom factor; Bb contains the active site. CC -!- Bb is formed by cleavage of proenzyme factor B by factor D. CC -!- Cleavage of complement component C5 requires additional C3b which CC binds C5 and renders it susceptible to cleavage by C3b,Bb complex. CC -!- C3b,Bb is stabilized in plasma by factor P. CC -!- Belongs to peptidase family S1. DR P81187, CFAB_BOVIN ; Q864V9, CFAB_GORGO ; P00751, CFAB_HUMAN ; DR P04186, CFAB_MOUSE ; Q864W0, CFAB_PANTR ; Q03710, CFAB_PIG ; DR Q864W1, CFAB_PONPY ; //