The PA clan (P roteases of mixed nucleophile, superfamily A ) is the largest group of proteases with common ancestry as identified by structural homology . Members have a chymotrypsin -like fold and similar proteolysis mechanisms but can have identity of <10%. The clan contains both cysteine and serine proteases (different nucleophiles ).[ 1] [ 2] PA clan proteases can be found in plants ,[ 3] animals ,[ 3] fungi ,[ 3] eubacteria ,[ 4] archaea [ 5] [ 6] and viruses .[ 2]
The common use of the catalytic triad for hydrolysis by multiple clans of proteases, including the PA clan, represents an example of convergent evolution .[ 7] The differences in the catalytic triad within the PA clan is also an example of divergent evolution of active sites in enzymes.[ 2]
^ Rawlings ND, Barrett AJ, Bateman A (January 2012). "MEROPS: the database of proteolytic enzymes, their substrates and inhibitors" . Nucleic Acids Research . 40 (Database issue): D343-50. doi :10.1093/nar/gkr987 . PMC 3245014 . PMID 22086950 .
^ a b c Bazan JF, Fletterick RJ (November 1988). "Viral cysteine proteases are homologous to the trypsin-like family of serine proteases: structural and functional implications" . Proceedings of the National Academy of Sciences of the United States of America . 85 (21): 7872–6. Bibcode :1988PNAS...85.7872B . doi :10.1073/pnas.85.21.7872 . PMC 282299 . PMID 3186696 .
^ a b c Laskar A, Rodger EJ, Chatterjee A, Mandal C (May 2012). "Modeling and structural analysis of PA clan serine proteases" . BMC Research Notes . 5 : 256. doi :10.1186/1756-0500-5-256 . PMC 3434108 . PMID 22624962 .
^ Barbosa JA, Saldanha JW, Garratt RC (July 1996). "Novel features of serine protease active sites and specificity pockets: sequence analysis and modelling studies of glutamate-specific endopeptidases and epidermolytic toxins" . Protein Engineering . 9 (7): 591–601. doi :10.1093/protein/9.7.591 . PMID 8844831 .
^ "MEROPS - Archaeal S01 proteases" .[permanent dead link ]
^ Ruiz-Perez F, Nataro JP (March 2014). "Bacterial serine proteases secreted by the autotransporter pathway: classification, specificity, and role in virulence" . Cellular and Molecular Life Sciences . 71 (5): 745–70. doi :10.1007/s00018-013-1355-8 . PMC 3871983 . PMID 23689588 .
^ Buller AR, Townsend CA (February 2013). "Intrinsic evolutionary constraints on protease structure, enzyme acylation, and the identity of the catalytic triad" . Proceedings of the National Academy of Sciences of the United States of America . 110 (8): E653-61. Bibcode :2013PNAS..110E.653B . doi :10.1073/pnas.1221050110 . PMC 3581919 . PMID 23382230 .