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C5938 Sigma

Complement factor I from human plasma

>90% (SDS-PAGE)



Biochem/physiol Actions

Protease which cleaves and inactivates C3b and C4b

Other Notes

View more information on the complement pathway at www.sigma-aldrich.com/enzymeexplorer

Physical form

Supplied as a 1mg/ml solution in PBS, pH 7.2


Complement factor I from human plasma has been used in a case study of glucose-starved Staphylococcus aureus. Complement factor I from human plasma has also been used to study the human complement cascade of proteolysis as a target of laser irradiation.

Price and Availability

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≥3000 C3H50 units/mg (using C3 deficient serum)

90-110 μg/mL in PBS, pH 7.2, ≥90% (SDS-PAGE)

1 mg/mL in PBS, pH 7.2, ≥90% (SDS-PAGE)

Safety & Documentation

Safety Information

Safety Information for this product is unavailable at this time.


Certificate of Analysis

Certificate of Origin

Protocols & Articles


Plasma Derived Proteins and Enzymes

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Peer-Reviewed Papers


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Factor H-related protein 4 activates complement by serving as a platform for the assembly of an alternative pathway C3 convertase via its interaction with C3b Hebecker, M. and M. Jozsi J. Biol. Chem. 287(23), 19258-36, (2012)

Life and death of proteins: A case study of glucose-starved Staphylococcus aureus Michalik, S., et al. Mol. Cell. Proteomics 11(9), 558-70, (2012)


The study of the human complement cascade of proteolysis as a target of laser irradiation Galebskaia, L., et al. Biomed. Khim. 55, 68-72, (2012)

Human complement C3b inactivator: isolation, characterization, and demonstration of an absolute requirement for the serum protein beta1H for cleavage of C3b and C4b in solution. Pangburn, M.K., et al. J. Exp. Med. 146, 257, (1977)


Immune evasion of Enterococcus faecalis by an extracellular gelatinase that cleaves C3 and iC3b. Park, S.Y., et al. J. Histochem. Cytochem. 181, 6328-36, (2008)


Alzheimer risk associated with a copy number variation in the complement receptor 1 increasing C3b/C4b binding sites. Brouwers N, Van Cauwenberghe C, Engelborghs S, et al. Mol. Psychiatry 17(2), 223-33, (2012)


Risk alleles in CFH and ARMS2 are independently associated with systemic complement activation in age-related macular degeneration. Smailhodzic D, Klaver CC, Klevering BJ, et al. Ophthalmology 119(2), 339-46, (2012)


Protection of nonself surfaces from complement attack by factor H-binding peptides: implications for therapeutic medicine. Wu YQ, Qu H, Sfyroera G, et al. J. Immunol. 186(7), 4269-77, (2011)


Complement activation in diseases presenting with thrombotic microangiopathy. Meri S Eur. J. Intern. Med. 24(6), 496-502, (2013)


Membranoproliferative glomerulonephritis with C3NeF and genetic complement dysregulation. Leroy V, Fremeaux-Bacchi V, Peuchmaur M, et al. Pediatr. Nephrol. 26(3), 419-24, (2011)


Complement factor I in health and disease. Nilsson SC, Sim RB, Lea SM, et al. Mol. Immunol. 48(14), 1611-20, (2011)


The novel complement inhibitor human CUB and Sushi multiple domains 1 (CSMD1) protein promotes factor I-mediated degradation of C4b and C3b and inhibits the membrane attack complex assembly. Escudero-Esparza A, Kalchishkova N, Kurbasic E, et al. FASEB J. 27(12), 5083-93, (2013)


Genetic, behavioral, and sociodemographic risk factors for second eye progression in age-related macular degeneration. Lechanteur YT, van de Ven JP, Smailhodzic D, et al. Invest. Ophthalmol. Vis. Sci. 53(9), 5846-52, (2012)


Acquisition of complement inhibitor serine protease factor I and its cofactors C4b-binding protein and factor H by Prevotella intermedia. Malm S, Jusko M, Eick S, et al. PLoS ONE 7(4), e34852, (2012)


Rare variants in CFI, C3 and C9 are associated with high risk of advanced age-related macular degeneration. Seddon JM, Yu Y, Miller EC, et al. Nat. Genet. 45(11), 1366-70, (2013)


Molecular organization and function of the complement system. Müller-Eberhard HJ Annu. Rev. Biochem. 57, 321-47, (1988)


Mutations in complement regulatory proteins predispose to preeclampsia: a genetic analysis of the PROMISSE cohort. Salmon JE, Heuser C, Triebwasser M, et al. PLoS Med. 8(3), e1001013, (2011)


Eculizumab for dense deposit disease and C3 glomerulonephritis. Bomback AS, Smith RJ, Barile GR, et al. Clin. J. Am. Soc. Nephrol. 7(5), 748-56, (2012)


Factor I autoantibodies in patients with atypical hemolytic uremic syndrome: disease-associated or an epiphenomenon? Kavanagh D, Pappworth IY, Anderson H, et al. Clin. J. Am. Soc. Nephrol. 7(3), 417-26, (2012)


Cleavage of C4b by C3b inactivator: production of a nicked form of C4b, C4b', as an intermediate cleavage product of C4b by C3b inactivator. Nagasawa S, Ichihara C, and Stroud RM J. Immunol. 125(2), 578-82, (1980)


Structural basis for complement factor I control and its disease-associated sequence polymorphisms. Roversi P, Johnson S, Caesar JJ, et al. Proc. Natl. Acad. Sci. U. S. A. 108(31), 12839-44, (2011)


Complement factor I deficiency: a not so rare immune defect: characterization of new mutations and the first large gene deletion. Alba-Domínguez M, López-Lera A, Garrido S, et al. Orphanet J. Rare Dis. 7, 42, (2012)


Plasma levels of complement proteins from the alternative pathway in patients with age-related macular degeneration are independent of Complement Factor H Tyr⁴⁰²His polymorphism. Silva AS, Teixeira AG, Bavia L, et al. Mol. Vis. 18, 2288-99, (2012)


Neisseria meningitidis NalP cleaves human complement C3, facilitating degradation of C3b and survival in human serum. Del Tordello E, Vacca I, Ram S, et al. Proc. Natl. Acad. Sci. U. S. A. 111(1), 427-32, (2014)


Analysis of binding sites on complement factor I using artificial N-linked glycosylation. Sanchez-Gallego JI, Groeneveld TW, Krentz S, et al. J. Biol. Chem. 287(17), 13572-83, (2012)


A hypervariable STR polymorphism in the CFI gene: southern origin of East Asian-specific group H alleles. Yuasa I, Jin F, Harihara S, et al. Leg. Med. (Tokyo.) 15(5), 239-43, (2013)


Molecular characterization of two novel cases of complete complement inhibitor Factor I deficiency. Nita IM, Genel F, Nilsson SC, et al. Mol. Immunol. 48(8), 1068-72, (2011)


Age-related penetrance of hereditary atypical hemolytic uremic syndrome. Sullivan M, Rybicki LA, Winter A, et al. Ann. Hum. Genet. 75(6), 639-47, (2011)


Common genetic variants in complement genes other than CFH, CD46 and the CFHRs are not associated with aHUS. Ermini L, Goodship TH, Strain L, et al. Mol. Immunol. 49(4), 640-8, (2012)


Species selectivity in poxviral complement regulators is dictated by the charge reversal in the central complement control protein modules. Yadav VN, Pyaram K, Ahmad M, et al. J. Immunol. 189(3), 1431-9, (2012)


C3b inactivator and beta 1H. Crossley LG Meth. Enzymol. 80 Pt C, 112-24, (1981)


Tetartohedral twinning could happen to you too. Roversi P, Blanc E, Johnson S, et al. Acta Crystallogr. D Biol. Crystallogr. 68(Pt 4), 418-24, (2012)


Activation of innate anti-viral immune response genes in symptomatic benign prostatic hyperplasia. Madigan AA, Sobek KM, Cummings JL, et al. Genes Immun. 13(7), 566-72, (2012)


Dissection of functional sites in herpesvirus saimiri complement control protein homolog. Reza MJ, Kamble A, Ahmad M, et al. J. Virol. 87(1), 282-95, (2013)


Mutations of complement factor I and potential mechanisms of neuroinflammation in acute hemorrhagic leukoencephalitis. Broderick L, Gandhi C, Mueller JL, et al. J. Clin. Immunol. 33(1), 162-71, (2013)


The genetics of the alternative pathway of complement in the pathogenesis of HELLP syndrome. Crovetto F, Borsa N, Acaia B, et al. J. Matern. Fetal. Neonatal. Med. 25(11), 2322-5, (2012)


Diagnosis and classification of hemolytic uremic syndrome: the Hungarian experience. Reusz GS, Szabó AJ, Réti M, et al. Transplant. Proc. 43(4), 1247-9, (2011)


No evidence of association between complement factor I genetic variant rs10033900 and age-related macular degeneration. Cipriani V, Matharu BK, Khan JC, et al. Eur. J. Hum. Genet. 20(1), 1-2; author reply 3, (2012)


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