title: Inactivation of calpain I and calpain II by specificity-oriented tripeptidyl chloromethyl ketones.
abstract: Three new tripeptidyl chloromethyl ketones, Leu-Leu-XCH2Cl, with X representing Phe, Tyr, or Lys, were synthesized and their potencies to inactivate calpains I and II were compared. They were designed to fulfil the specificity requirement of calpains established recently. When compared in terms of the dose for 50% inactivation, Leu-Leu-PheCH2Cl was the strongest inactivator, being 500-600 times more effective than tosyl-PheCH2Cl and 5-14 times more than N-[N-(L-3-trans-carboxyoxiran-2-carbonyl)-L-leucyl]agmatine (E-64). The potency toward calpain, either I or II, decreased in the order Phe greater than Tyr greater than Lys derivatives greater than E-64, whereas that toward papain was E-64 greater than Lys greater than Phe greater than Tyr derivatives. From the determined kinetic parameters, the Phe derivative was 18.3 and 16.6 times more effective than E-64 on calpains I and II, respectively. Likewise, the rate of the alkylation reaction by these chloromethyl ketones with calpain I was 2-4 times greater than that with calpain II. Leu-Leu-PheCH2Cl and its N-dansylated product should be useful for highly selective affinity labeling of calpains I and II.
mesh_terms: D000478:Alkylation; D000590:Amino Acid Chloromethyl Ketones / Q000138:chemical synthesis / Q000494:pharmacology*; D002154:Calpain / Q000037:antagonists & inhibitors*; D002364:Caseins / Q000494:pharmacology; D007700:Kinetics; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D002364:Caseins; D014108:Tosylphenylalanyl Chloromethyl Ketone; D002154:Calpain