<prompt> C-3 convease in alternate complement pathway ?C4b2aC3bC3bBbC3a  <response>: Ans. is c i.e., C3bBb . The central process in the complement cascade both in classical and alternative pathway is the activation of C3 by C3-convease. . In classical pathway C3-convease is C4b2a and in alternative pathway C3-convease is C3bBb. 