A recombinant human stromelysin catalytic domain identifying tryptophan derivatives as human stromelysin inhibitors

The human stromelysin catalytic domain (SCD) has been expressed in Escherichia coli and purified to homogeneity (Ye et al. Biochemistry 1992, 31, 11231). We have used this recombinant SCD for inhibitor screening and identified tryptophan derivatives as competitive inhibitors of SCD. Both Cbz-L-Trp-OH (1, IC50 2.5 microM, Ki 2.1 microM) and Boc-L-Trp-OH (3, IC50 10 microM, Ki 8 microM) showed good inhibitory activity. Modification at the indole nitrogen with formyl or mesitylene-2-sulfonyl group (16, IC50 34 microM, Ki 28 microM; 17, IC50 63 microM, Ki 52 microM) showed reduced activity. The amide Cbz-L-Trp-NH2 (13) was not active, but esters Cbz-L-Trp-OSu (14, IC50 13 microM, Ki 11 microM) and Boc-L-Trp-OSu (15, IC50 102 microM, Ki 84 microM) showed activity. Aromatic amino acid derivatives Cbz-L-Tyr-OH (18, IC50 24 microM, Ki 20 microM) and Cbz-L-Phe-OH (26, IC50 40 microM, Ki 33 microM) were also active, but other amino acid derivatives had no activity. Although Cbz-D-Trp-OH (2, IC50 86 microM, Ki 71 microM) was active, the L-configuration is consistently preferred for inhibitory activity. Some of the SCD inhibitors were tested on full-length human stromelysin purified from cultured human cells, and they showed the same potency rank order. These results demonstrate the usefulness of recombinant DNA technology in generating the authentic human protein with improved properties for drug discovery.