Complement Factor I

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** Complement factor I (583 aa, ~66 kDa) is encoded by the human CFI gene. This protein is involved in proteolytic inactivation of the alpha-chain of C3d and the alpha-chain of C4b, which leads to inhibition of the complement cascade.

**Synonyms:** - C3B/C4B Inactivator - CFI - Complement Component I - Complement Control Protein Factor I - EC 3.4.21.45