C1 esterase inhibitor

C1 es·ter·ase in·hib·i·tor

an α2-neuraminoglycoprotein that inhibits the enzymatic activity of C1 esterase, the activated first component of complement. A deficiency of this inhibitor results in a lack of inhibition of C1r and C1s leading to uncontrolled activation of the complement cascade and angioedema.

SERPING1

A gene on chromosome 11q12-q13.1 that encodes a highly glycosylated plasma protein which regulates the complement cascade by inhibiting activated C1r and C1s, thereby preventing complement activation.
Molecular pathology
C1-INH/SERPING1 deficiency is associated with hereditary angioneurotic oedema (HANE).