A caged substrate peptide for matrix metalloproteinases

Based on the widely applied fluorogenic peptide FS-6 (Mca-Lys-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2; Mca = methoxycoumarin-4-acetyl; Dpa = N-3-(2,4-dinitrophenyl)l-?,?-diaminopropionyl) a caged substrate peptide Ac-Lys-Pro-Leu-Gly-Lys*-Lys-Ala-Arg-NH2 (*, position of the cage group) for matrix metalloproteinases was synthesized and characterized. The synthesis implies the modification of a carbamidated lysine side-chain amine with a photocleavable 2-nitrobenzyl group. Mass spectrometry upon UV irradiation demonstrated the complete photolytic cleavage of the protecting group. Time-resolved laser-flash photolysis at 355 nm in combination with transient absorption spectroscopy determined the biphasic decomposition with ?a = 171 ± 3 ms (79%) and ?b = 2.9 ± 0.2 ms (21%) at pH 6.0 of the photo induced release of the 2-nitrobenzyl group. The recombinantly expressed catalytic domain of human membrane type I matrix metalloproteinase (MT1-MMP or MMP-14) was used to determine the hydrolysis efficiency of the caged peptide before and after photolysis. It turned out that the cage group sufficiently shields the peptide from peptidase activity, which can be thus controlled by UV light.