Fig. 4: Cleavage of C3 by C3 Convertase during the Classical Complement Pathway

The C4b2a functions as a C3 convertase that can enzymatically cleave hundreds of molecules of C3 into C3a and C3b. C3b, and to a lesser extent C4b, attaches antigens to phagocytes for opsonization (enhanced attachment). One portion of the C3b binds to proteins and polysaccharides on microbial surfaces; another portion binds to CR1 receptors on phagocytes, B-lymphocytes, and dendritic cells. This results in improved phagocytosis. C3a can promote inflammatory responses that enable body defense cells and defense chemicals to leave the blood and enter the tissues.

Illustration of Cleavage of C3 by C3 Convertase during the Classical Complement Pathway .jpg by Gary E. Kaiser, Ph.D.
Professor of Microbiology, The Community College of Baltimore County, Catonsville Campus
This work is licensed under a Creative Commons Attribution 4.0 International License.
Based on a work at https://cwoer.ccbcmd.edu/science/microbiology/index_gos.html.

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Last updated: August, 2019
Please send comments and inquiries to Dr. Gary Kaiser