title: Inhibitions by E-64 derivatives of rat liver cathepsin B and cathepsin L in vitro and in vivo.
abstract: The mechanism of inhibition of cathepsin B [EC 3.4.22.1] and cathepsin L [EC 3.4.22.-] by E-64 was investigated. Kinetic studies indicated that E-64 was an irreversible inhibitor of these enzymes. [3H]E-64 is incorporated into cathepsin B in a one/one molar ratio in parallel with inactivation of the enzyme. Titration of one of the 10 SH groups of native cathepsin B with 2,2'-dithiodipyridine resulted in complete loss of enzyme activity. Decrease of titratable SH groups and activity of cathepsin B was proportional to the concentration of E-64 added, indicating that E-64 binds to an equimolar amount of active SH residues of cathepsin B. The effects of E-64 and its derivatives on lysosomal cathepsin B and cathepsin L in rat liver were studied in vitro and in vivo. The D form of E-64 inhibited the cathepsin both in vitro and in vivo, although its inhibitory effects were less than those of E-64-(L). E-64-b(RR), in which the terminal agmatine of E-64 is replaced by leucine, was as active as E-64-(L) in vitro, but was completely inactive in vivo. Among the E-64 derivatives tested, E-64-c(SS), in which the terminal agmatine of E-64 is replaced by isoarylamide, showed strong inhibitory activity in vivo, like E-64-(L).
mesh_terms: D000376:Agmatine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002401:Cathepsin B; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors*; D003546:Cysteine Endopeptidases; D010450:Endopeptidases; D006146:Guanidines / Q000494:pharmacology*; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D008247:Lysosomes / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D006146:Guanidines; D011480:Protease Inhibitors; D013438:Sulfhydryl Compounds; D000376:Agmatine; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L; C534280:Ctsl protein, rat; D007930:Leucine; C024974:E 64