Chemicals and Drugs

Complement Factor I

A plasma serine proteinase that cleaves the alpha-chains of C3b and C4b in the presence of the cofactors COMPLEMENT FACTOR H and C4-binding protein, respectively. It is a 66-kDa glycoprotein that converts C3b to inactivated C3b (iC3b) followed by the release of two fragments, C3c (150-kDa) and C3dg (41-kDa). It was formerly called KAF, C3bINF, or enzyme 3b inactivator.

National Library of MedicineMedical Subject Headings2026

Structured Summary

Abstract

A plasma serine proteinase that cleaves the alpha-chains of C3b and C4b in the presence of the cofactors COMPLEMENT FACTOR H and C4-binding protein, respectively. It is a 66-kDa glycoprotein that converts C3b to inactivated C3b (iC3b) followed by the release of two fragments, C3c (150-kDa) and C3dg (41-kDa). It was formerly called KAF, C3bINF, or enzyme 3b inactivator.

MeSH Record

Classification

Related Concepts

Knowledge Graph

Loading graph…

Drag nodes to rearrange; hover to trace links; click a node to open its page.

Drug Class

Pharmacological Action

MeSH Record

Synonyms

14 entry terms
  • C3b Inactivator
  • C3b-C4b Inactivator
  • C4b-C3b-INA
  • C4bC3bINA
  • Complement 3b-Complement 4b Inactivator
  • Complement C4b-C3b Inactivator
  • C3b C4b Inactivator
  • C4b C3b INA
  • C4b-C3b Inactivator, Complement
  • Complement 3b Complement 4b Inactivator
  • Complement C4b C3b Inactivator
  • Inactivator, C3b
  • Inactivator, C3b-C4b
  • Inactivator, Complement C4b-C3b

MeSH Record

Aspects Covered

29 allowable subheadings

Indexed with the subheadings administration & dosage, adverse effects, agonists, analysis, antagonists & inhibitors, biosynthesis, cerebrospinal fluid, chemical synthesis, chemistry, classification, deficiency, drug effects, economics, genetics, history, immunology, isolation & purification, metabolism, pharmacokinetics, pharmacology, physiology, poisoning, radiation effects, standards, supply & distribution, therapeutic use, toxicity, ultrastructure, urine.

MeSH Record

Indexing Annotation

do not confuse with FACTOR I see FIBRINOGEN

MeSH Record

History Note

93; was FACTOR I, C 3B INACTIVATOR (NM) 1983-92

MeSH Record

Previous Indexing

  • Peptide Peptidohydrolases (1983-1987)
  • Serine Proteinases (1988-1992)

MeSH Hierarchy

Tree Numbers

AMA Style

References

  1. National Library of Medicine. Complement Factor I. Medical Subject Headings (MeSH). 2026. Unique ID D017244. http://id.nlm.nih.gov/mesh/2026/D017244
  2. Complement Factor I. In: Wikidata. https://www.wikidata.org/wiki/Q5156413