Selective inhibition of Trypsin by (2R,4R)-4-Phenyl-1-[N-alpha-(7-methoxy-2-naphthalenesulfonyl)-L-arginyl]-2-piperidinecarboxylic acid

Evidence is accumulating indicating that trypsin stimulates divergent cellu lar reactions through the proteinase-activated receptor, in addition to its role as the digestive enzyme. In this report, we introduce (2R,4R)-4-pheny l-1-[N-alpha-(7-methoxy-2-naphthalenesulfonyl)-L-arginyl]-2-piperidinecarbo xylic acid as a potent and selective trypsin inhibitor. The agent inhibited trypsin competitively with the K-i value of 0.1 mu M. It inhibited thrombi n weakly (K-i = 2 mu M) and did not inhibit plasmin, plasma kallikrein, uro kinase, and mast cell tryptase (K-i values for these enzymes are >60 mu M). Comparative studies with several established proteinase inhibitors reveale d that the compound was the first small molecular weight trypsin inhibitor without tryptase inhibitory activity. A docking study has provided a plausi ble explanation for the molecular mechanism of the selective inhibition sho wing that the agent fits into the active site of trypsin without any severe collision but that it comes into clash at the 4-phenyl group of piperidine ring against the "60-insertion loop" of thrombin and at the 7-methoxy-2-na phthalenesulfonyl group against Gln(98) of tryptase.