3.4.21.45: complement factor I
This is an abbreviated version!
For detailed information about complement factor I, go to the full flat file.
Word Map on EC 3.4.21.45
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3.4.21.45
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hemolytic
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convertase
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macular
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properdin
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uremic
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cell-bound
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c3d
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fluid-phase
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glomerulonephritis
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complement-mediated
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opsonization
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medicine
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i-mediated
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eculizumab
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alpha\'-chain
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c4-binding
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c4bp
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microangiopathic
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opsonin
- 3.4.21.45
-
hemolytic
-
convertase
-
macular
- properdin
-
uremic
-
cell-bound
- c3d
-
fluid-phase
- glomerulonephritis
-
complement-mediated
-
opsonization
- medicine
-
i-mediated
- eculizumab
-
alpha\'-chain
-
c4-binding
- c4bp
-
microangiopathic
-
opsonin
Reaction
Inactivates complement subcomponents C3b, iC3b and C4b by proteolytic cleavage =
Synonyms
C3b inactivator, C3b/C4b inactivator, C3bINA, CFI, complement C3b inactivator, complement C3b/C4b inactivator, complement C4b inactivator, complement C4bi, complement compoment C3b inactivator, complement factor I, complement inhibitor factor I, complement regulator factor I, conglutinogen-activating factor C, factor I, factor I-like activity, fI, GcIf-1, GcIf-2, GcIf-3, GcIf-4, IF, plasma protease factor I, serine protease Factor I
ECTree
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General Information
General Information on EC 3.4.21.45 - complement factor I
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malfunction
physiological function
additional information
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mutations in complement factor I affect both secretion and function of complement factor I, which leads to impaired regulation of the complement system in atypical hemolytic uremic syndrome
malfunction
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two mutations, G17V and C196S, in the enzyme are identified in patients, which result in failure to secrete the enzyme, phenotype with high C3, membrane attack complex, and interleukin-1 levels in the brain and perivascular hemorrhagic necrosis, subacute inflammation in the subcortical white matter, patchy demyelination and an inflammatory infiltrate with a neutrophilic and histiocytic predominance, overview. Mutations of complement factor I and potential mechanisms of neuroinflammation in acute hemorrhagic leukoencephalitis, overview
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the interaction of clumping factor A with factor I contributes to Staphylococcus aureus virulence by a complement-mediated mechanism
physiological function
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factor I is in a proteolytically inactive form, it circulates in a zymogen-like state despite being fully processed to the mature sequence. This inactive form is maintained by the noncatalytic heavy-chain allosterically modulating activity of the light chain. Once the ternary complex of factor I, a cofactor and a substrate is formed, the allosteric inhibition is released, and factor I is oriented for cleavage. General model for factor I regulation of complement predicts that binding of the cofactor to C3b produces a stable platform onto which the factor I can dock, binding of factor I releases the allosteric inhibitory effects of the heavy chain and induces remodeling of the zymogen-activation domain and the active site forms around the substrate loop for the primary cleavage event
physiological function
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factor I is a serine protease that inhibits all complement pathways by degrading activated complement components C3b and C4b. It functions only in the presence of several cofactors, such as factor H, C4b-binding protein, complement receptor 1, and membrane cofactor protein
physiological function
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the factor I activity in Nipah virus inhibits human complement pathways through cleavage of C3b
physiological function
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the serine protease Factor I (FI) is the central inhibitor of complement degrading complement components C3b and C4b in the presence of cofactors such as C4b binding protein (C4BP) and factor H (FH). The selective enzyme binding by the bacterium Prevotella intermedia in human serum represents a distinct mechanism contributing to complement evasion by a Gram-negative bacterial pathogen associated with chronic diseases. Binding of enzyme cofactors C4BP and FH by Prevotella intermedia ATCC 25611 leads to increased degradation of C4b and C3b, respectively
physiological function
the enzyme plays an important role in Cynoglossus semilaevis immunity and shows broad-spectrum antimicrobial activities against the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and Shewanella putrefaciens
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the enzyme can be selectively bound by Prevotella intermedia ATCC 25611 cells, the bound enzyme retains its serine protease activity, interaction analysis, overview
additional information
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the Nipah virus is completely resistant to in vitro neutralization by normal human serum