Limited proteolysis of C1 inhibitor (C1-INH) by neutrophil elastase, Pseudomonas elastase and snake venoms resulted in initial cleavage within the molecule's N-terminus followed by further cleavage within the molecule's C-terminally placed reactive centre. N-Terminal proteolysis occurred at peptide bonds 14-15, 36-37 and 40-41. This had no effect on either the inhibitory activity or the heat-stability of C1-INH. Proteolysis within the reactive centre occurred at peptide bonds 439-440, 440-441, 441-442 and 442-443. Cleavage at any one of these sites inactivated C1-INH and conferred enhanced heat-stability upon a previously heat-labile molecule. Released neutrophil proteinases also cleaved and inactivated C1-INH, suggesting that they may physiologically regulate C1-INH during inflammatory episodes.
Research Article|February 15 1989
The structural basis for neutrophil inactivation of C1̅ inhibitor
P A Pemberton;
R A Harrison;
P J Lachmann;
Biochem J (1989) 258 (1): 193-198.
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P A Pemberton, R A Harrison, P J Lachmann, R W Carrell; The structural basis for neutrophil inactivation of C1̅ inhibitor. Biochem J 15 February 1989; 258 (1): 193–198. doi: https://doi.org/10.1042/bj2580193
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