The matrix metalloproteinases (MMPs) family consists of over 23 structurally related endopeptidases [1]. These enzymes are known to participate in cancer progression and metastasis which make them very attractive molecular targets for the design of selective chemical probes [2]. Of the various MMPs known to be involved in cancer, MMP-2 (gelatinase A) and MMP-9 (gelatinase B) are of special interest since their overexpression is correlated with tumor aggressiveness and a poor prognosis. What is more, the elevated level of these proteins has been found in bladder, brain, breast, colorectal, lung, pancreas and prostate cancers [3].
So far several peptide-based fluorescent substrates for MMP-2 and MMP-9 have been reported in the literature, however none of them displays an absolute specificity toward only one MMP of interest[4,5]. The main limitation of these substrates is that only natural amino acids were use in their structures. Our group has recently demonstrated that the use of a wide range of unnatural amino acids in peptidic substrates can solve the problem regarding proteases overlapping substrate specificity[6].
In the present study we demonstrate a two-step approach for the design of novel and very selective substrates that can distinguish between MMP-2 and MMP-9. In the first step we extracted from the literature and synthesized over 40 "the most specific so far" MMP-2 and MMP-9 sequences (natural protein substrates, synthetic constructs), and by measuring their kinetic parameters we selected two lead structures: one for MMP-2 and one for MMP-9. In the second step, based on these sequences we synthesized two tailored internally quenched fluorogenic libraries containing natural and a wide range of unnatural amino acids. The kinetic analysis of these libraries allowed us to develop the most specific so far MMP-2 and MMP-9 chemical probes.
This work was supported by the National Science Centre grant 2014/13/B/ST5/00240in Poland