METHOD FOR DETERMINING THE ACTIVITY OF TRANSGLUTAMINASE FACTOR XIIIA

Spectroscopic process for UV/visual- or fluorescence-based kinetic determination of the activity of transglutaminases, preferably transglutaminase factor XIIIa, comprises splitting the factor XIIIa of a modified peptide substrate (I) and determining the resulting change in UV/visual or the fluorescence at appropriate wavelengths. Spectroscopic process for UV/visual- or fluorescence-based kinetic determination of the activity of transglutaminases, preferably transglutaminase factor XIIIa, comprises splitting the factor XIIIa of a modified peptide substrate of formula (I) and determining the resulting change in UV/visual or the fluorescence at appropriate wavelengths. R1 : (4-nitrophenyl)amino, (3-carboxy-4-nitro-phenyl)amino, (2-carboxy-4-nitro-phenyl)amino, (4-methyl-2-oxo-chromen-7-yl)amino, [4-(2-amino-2-oxo-ethyl)-2-oxo-chromen-7-yl]amino, 4-nitrophenoxy, (4-methyl-2-oxo-chromen-7-yl)oxy or [4-(carboxymethyl)-2-oxo-chromen-7-yl]amino; R2 : NH 2or OH; A : natural or synthetic alpha -amino acid or alpha -imino acid residue, which is coupled by a peptide bond and is unprotected on its alpha -amino- or alpha -imino group; and B1 : a peptide bond coupled peptide sequence consisting of 3-13 natural or synthetic amino acids or imino acids linked to one another via peptide bonds. Independent claims are included for: (1) identification of compounds that modulate factor XIIIa-activity, comprising contacting at least one compound with factor XIIIa and subsequently measuring the activity of the factors XIIIa, preferably for identifying compounds that modulate the activity of factor XIIIa increase or decrease, preferably for the identification of inhibitors of factor XIIIa; and (2) peptide substrate for factor XIIIa, having a structure of formula (X-Glu(p-nitroanilide(pNA))-Y1-Z-Y1-Y1-T) or (X-Glu(AMC)-Y1-Z-Y1-Y1-T), preferably His-Tyr-Glu(pNA)-Ser-Lys-Val-Ile-Gly-NH 2, His -Ile-Glu(pNA)-Val-Lys-Val-Ile-Gly-NH 2, His-Ala-Glu(pNA)-Val-Lys-Val-Ile-Gly-NH 2, His-Phe-Glu(pNA)-Val-Lys-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Lys-Lys-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Val-Lys-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Lys-Val-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Val-Lys-Val-Ile-NH 2, Tyr-Glu(pNA)-Ile-Lys-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Leu-Lys-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Val-Arg-Val-Ile-Gly-NH 2, His-Tyr-Glu(pNA)-Val-Lys-Val-Phe-NH 2or His-Lys-Glu(pNA)-Val-Lys-Val-Ile-Gly-NH 2, where in all the substrates, pNA moiety can be replaced by 7-amino-4-methyl coumarin (AMC) residue. X