classical-complement-pathway C3/C5 convertase complex
classical-complement-pathway c3/c5 convertase complex
"A heterodimeric protein complex that catalyzes the cleavage of complement components C3 and C5, and acts in the classical pathway of complement activation; consists of one monomer of C2a and one monomer of C4b; C2a is the catalytic subunit, but cannot catalyze cleavage alone."