Complement C1s (C1S) Human Enzyme

This gene encodes a serine protease, which is a major constituent of the human complement subcomponent C1. C1s associates with two other complement components C1r and C1q in order to yield the first component of the serum complement system. Defects in this gene are the cause of selective C1s deficiency. [provided by RefSeq, Mar 2009]

C1S: C1s B chain is a serine protease that combines with C1q and C1r to form C1, the first component of the classical pathway of the complement system. C1r activates C1s so that it can, in turn, activate C2 and C4. Defects in C1S are the cause of complement component C1s deficiency (C1SD). A rare defect resulting in C1 deficiency and impaired activation of the complement classical pathway. C1 deficiency generally leads to severe immune complex disease with features of systemic lupus erythematosus and glomerulonephritis. Belongs to the peptidase S1 family.

Protein type: Protease; EC 3.4.21.42

Chromosomal Location of Human Ortholog: 12p13

Cellular Component: extracellular region

Molecular Function: identical protein binding; protein binding; serine-type endopeptidase activity; calcium ion binding

Biological Process: innate immune response; proteolysis; complement activation, classical pathway; complement activation

Disease: Complement Component C1s Deficiency