Open AccessA model for the reaction mechanism of the transglutaminase 3 enzyme
Author(s) -
Bijan Ahvazi,
Peter M. Steinert
Publication year - 2003
Publication title -
experimental and molecular medicine/experimental and molecular medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.703
H-Index - 82
eISSN - 2092-6413
pISSN - 1226-3613
DOI - 10.1038/emm.2003.31
Subject(s) - tissue transglutaminase , glutamine , chemistry , enzyme , lysine , substrate (aquarium) , active site , docking (animal) , biochemistry , binding site , biophysics , stereochemistry , calcium , amino acid , biology , organic chemistry , medicine , ecology , nursing
Transglutaminase enzymes (TGases) catalyze the calcium dependent formation of an isopeptide bond between protein-bound glutamine and lysine substrates. Previously we have shown that activated TGase 3 acquires two additional calcium ions at site two and three. The calcium ion at site three results in the opening of a channel. At this site, the channel opening and closing could modulate, depending on which metal is bound. Here we propose that the front of the channel could be used by the two substrates for enzyme reaction. We propose that the glutamine substrate is directed from Trp236 into the enzyme, shown by molecular docking. Then a lysine substrate approaches the opened active site to engage Trp327, leading to formation of the isopeptide bond. Further, direct comparisons of the structures of TGase 3 with other TGases have allowed us to identify several residues that might potentially be involved in generic and specific recognition of the glutamine and lysine substrates.