Fibroblast collagenase (MMP-1), a member of the matrix metalloproteinases family, is believed to be a pathogenesis of arthritis, by cleaving triple-helical type II collagen in cartilage. From the similarity of the active site zinc binding mode with hydroxamate, we designed and synthesized a a-mercaptocarbonyl possessing compounds (3-5), which incorporated various peptide sequences as enzyme recognition sites. The P 4 -P 1 peptide incorporating compound (3) exhibited as potent inhibition as the hydroxamate (1) and the carboxylate (2) type inhibitors, with an IC 50 of 10 ؊6 M order against MMP-1. But the inhibitor (3) related compounds (6-8) displayed decreased or no inhibitory potencies. These results suggest that the existence of both the carbonyl and thiol groups might be critical for the inhibition, and the distance between the two functional groups is important for inhibitory potency. For P n peptide incorporating compounds (4a-k), except for 4h and 4k, all compounds showed IC 50 values under sub-nanomolar. Among them, for potent inhibition, Leu was better than Phe and Val as the P 1 amino acid, and the P 2 position amino acid was necessary, and preferentially Phe. Insertion of the P n peptide into 4d or 4k, giving compounds 5a-c, did not increase the activities of 4d and 4k. Substitution of the mercapto group with other functional groups lost the activity of compound 4a. The stereochemical preference at the thiol-attached position was also determined by preparation of both isomers of 4a. It was found that the S configuration compound (36b) is approximately 100 times more potent than the corresponding R-isomer (36a).Key words matrix metalloproteinase; inhibitor; a-mercaptocarbonyl; isoserine; in vitro activity Design The X-ray crystal structures of MMP-1 with bound inhibitors reveal that the hydroxamate acts as a bidentate ligand with each oxygen at an optimal distance (2.1-2.2 Å) from the active-site zinc ion (structure A, Fig. 2).
13)From this structural analysis data, we reasoned that the amercaptocarbonyl group (structure B) at the cleavage site would chelate at the active-site zinc ion by both carbonyl and mercapto groups in a similar manner as the hydroxamate (Fig. 2). In comparison with the hydroxamate possessing MMPs inhibitors, little is known about thiol group including compounds. But, previously Donald and colleagues developed a b-mercapto carbonyl group possessing compound that exhibited 10 Ϫ7 M order of IC 50 against MMP-1.14) The compound differs in the distance between the carbonyl and mercapto groups from the structure B. In addition, Baxter and colleagues have prepared the thiol containing inhibitors utilizing computer-aided drug design, expecting new interactions with MMP-8 by hydrogen bonds, e.g. Ser172 of MMP-8.15) These compounds exhibited potent inhibitions with an IC 50 of 10 Ϫ7 -10 Ϫ9 M against MMP-3, -8, -9, but were not tested on MMP-1. We designed three different compounds containing an a-mercaptocarbonyl group, based on the enzyme recognition sites. The P 4 -P 1 peptide incorporati...