Limulus clotting factor overbar C (EC 3.4.21.84 , factor C , limulus factor C ) is an enzyme .[ 1] [ 2] [ 3] This enzyme catalyses the following chemical reaction
Selective cleavage of -Arg103 -Ser- and -Ile124 -Ile- bonds in limulus clotting factor B to form factor overbar B .
Cleavage of -Pro-Arg- bonds in synthetic substrates
This enzyme is isolated from the hemocyte granules of the horseshoe crabs Limulus and Tachypleus , where it serves as a LPS endotoxin-sensitive trypsin type serine protease to protect the organism from bacterial infection, initiating a cascade leading to coagulin formation.[ 4] From the N-terminus to the C-terminus, the domains are:
This enzyme is useful in Limulus amebocyte lysate as the endotoxin-detecting element. It can be produced recombinantly.[ 5]
References
^ Nakamura T, Morita T, Iwanaga S (February 1986). "Lipopolysaccharide-sensitive serine-protease zymogen (factor C) found in Limulus hemocytes. Isolation and characterization" . European Journal of Biochemistry . 154 (3): 511– 21. doi :10.1111/j.1432-1033.1986.tb09427.x . PMID 3512266 .
^ Muta T, Miyata T, Misumi Y, Tokunaga F, Nakamura T, Toh Y, et al. (April 1991). "Limulus factor C. An endotoxin-sensitive serine protease zymogen with a mosaic structure of complement-like, epidermal growth factor-like, and lectin-like domains" . The Journal of Biological Chemistry . 266 (10): 6554– 61. doi :10.1016/S0021-9258(18)38153-5 . PMID 2007602 .
^ Tokunaga F, Nakajima H, Iwanaga S (January 1991). "Further studies on lipopolysaccharide-sensitive serine protease zymogen (factor C): its isolation from Limulus polyphemus hemocytes and identification as an intracellular zymogen activated by alpha-chymotrypsin, not by trypsin". Journal of Biochemistry . 109 (1): 150– 7. doi :10.1093/oxfordjournals.jbchem.a123337 . PMID 2016264 .
^ Iwanaga S (May 2007). "Biochemical principle of Limulus test for detecting bacterial endotoxins" . Proceedings of the Japan Academy. Series B, Physical and Biological Sciences . 83 (4): 110– 9. Bibcode :2007PJAB...83..110I . doi :10.2183/pjab.83.110 . PMC 3756735 . PMID 24019589 .
^ Maloney T, Phelan R, Simmons N (October 2018). "Saving the horseshoe crab: A synthetic alternative to horseshoe crab blood for endotoxin detection" . PLOS Biology . 16 (10): e2006607. doi :10.1371/journal.pbio.2006607 . PMC 6200278 . PMID 30312293 .
External links
Activity Regulation Classification Kinetics Types