Intramolecular crosslinking of monomeric fibrinogen by tissue transglutaminase

In addition to generating polymeric products from human fibrinogen, human erythrocyte transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) was shown to catalyze the intramolecular reaction of crosslinking two of the constituent chains within monomeric fibrinogen itself. This internally fused protein derivative contains appreciable amounts of the N epsilon-(gamma-glutamyl)lysine bridge peptide and displays the A alpha.gamma hybrid chain pattern of crosslinking, characteristic for the actions of tissue transglutaminases on fibrinogen. Diagnostic analysis in pathological situations, where such enzymes might have escaped from cells into the plasma environment, should include a search for the internally crosslinked soluble fibrinogen monomer.