title: The propensity for deamidation and transamidation of peptides by transglutaminase 2 is dependent on substrate affinity and reaction conditions.
abstract: Transglutaminase 2 (TG2) catalyzes cross-linking or deamidation of glutamine residues in peptides and proteins. The in vivo deamidation of gliadin peptides plays an important role in the immunopathogenesis of celiac disease (CD). Although deamidation is considered to be a side-reaction occurring in the absence of suitable amines or at a low pH, a recent paper reported the selective deamidation of the small heat shock protein 20 (Hsp20), suggesting that deamidation could be a substrate dependent event. Here we have measured peptide deamidation and transamidation in the same reaction to reveal factors that affect the relative propensity for the two possible products. We report that the propensity for deamidation by TG2 is both substrate dependent and influenced by the reaction conditions. Direct deamidation is favored for poor substrates and at low concentrations of active TG2, while indirect deamidation (i.e. hydrolysis of transamidated product) can significantly contribute to the deamidation of good peptide substrates at higher enzyme concentrations. Further, we report for the first time that TG2 can hydrolyze iso-peptide bonds between two peptide substrates. This was observed also for gliadin peptides introducing a novel route for the generation of deamidated T cell epitopes in celiac disease.
authors.affiliation: Centre for Immune Regulation, Institute of Immunology, Rikshospitalet University Hospital, N-0027 Oslo, Norway. Jorunn.Stamnas@rr-research.no
authors.forename: Jorunn
authors.initials: J
authors.lastname: Stamnaes
authors.forename: Burkhard
authors.initials: B
authors.lastname: Fleckenstein
authors.forename: Ludvig M
authors.initials: LM
authors.lastname: Sollid
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D018984:Epitopes, T-Lymphocyte / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005903:Gliadin / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D050886:HSP20 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006860:Hydrogen Bonding; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D011392:Proline / Q000378:metabolism / Q000502:physiology; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D013379:Substrate Specificity; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D018984:Epitopes, T-Lymphocyte; D050886:HSP20 Heat-Shock Proteins; D010446:Peptide Fragments; D005973:Glutamine; D005903:Gliadin; D011392:Proline; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins
references.citation: Biochem J. 2002 Dec 1;368(Pt 2):377-96
references.pmid: 12366374
references.citation: FEBS Lett. 2004 Oct 8;576(1-2):57-62
references.pmid: 15474010
references.citation: J Biol Chem. 1997 Apr 11;272(15):10311-7
references.pmid: 9092583
references.citation: Connect Tissue Res. 2000;41(1):1-27
references.pmid: 10826705
references.citation: Biophys J. 2000 Jun;78(6):3240-51
references.pmid: 10828000
references.citation: Nat Med. 1997 Jul;3(7):797-801
references.pmid: 9212111
references.citation: Protein Sci. 1994 Jul;3(7):1131-5
references.pmid: 7920263
references.citation: Eur J Immunol. 2001 May;31(5):1317-23
references.pmid: 11465088
references.citation: Proteins. 2006 Mar 1;62(4):1044-52
references.pmid: 16385579
references.citation: Biochemistry. 2002 Jan 8;41(1):386-93
references.pmid: 11772038
references.citation: PLoS Biol. 2007 Dec;5(12):e327
references.pmid: 18092889
references.citation: J Exp Med. 2000 Feb 21;191(4):603-12
references.pmid: 10684852
references.citation: J Immunol. 2005 Feb 1;174(3):1657-63
references.pmid: 15661929
references.citation: Eur J Biochem. 1999 Jun;262(3):672-9
references.pmid: 10411627
references.citation: Trends Biochem Sci. 2002 Oct;27(10):534-9
references.pmid: 12368090
references.citation: Adv Enzymol Relat Areas Mol Biol. 1983;54:1-56
references.pmid: 6133417
references.citation: J Biol Chem. 2002 Sep 13;277(37):34109-16
references.pmid: 12093810
references.citation: Science. 1994 Jun 10;264(5165):1593-6
references.pmid: 7911253
references.citation: PLoS One. 2008 Mar 26;3(3):e1861
references.pmid: 18365016
references.citation: Nat Rev Mol Cell Biol. 2003 Feb;4(2):140-56
references.pmid: 12563291
references.citation: Clin Sci (Lond). 1985 May;68(5):573-9
references.pmid: 2858282
references.citation: J Biol Chem. 1997 Aug 15;272(33):20471-8
references.pmid: 9252357
references.citation: Science. 2002 Sep 27;297(5590):2275-9
references.pmid: 12351792
references.citation: J Exp Med. 2002 Mar 4;195(5):643-9
references.pmid: 11877487
references.citation: J Cell Biol. 2000 Feb 21;148(4):825-38
references.pmid: 10684262