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Description

A cell-permeable dipeptidylboronate compound that selectively inhibits 20S proteasome beta5 ChTL/chymotrypsin- over beta1 CL/caspase- and beta2 TL/trypsin-like activity (kinact/Ki = 38,000, 5,700, and <100 M-1s-1, respectively, in human 20S proteasome assays using 10 M Suc-LLVY-AMC/Cat. No. 539142, 10 M Z-LLE-AMC/Cat. No. 539141, or 50 M Boc-LRR-AMC as substrate) via a covalent, slowly reversible manner, displaying much reduced potency against human chymotrypsin, cathepsin G, leukocyte elastase, and thrombin (Ki = 0.32, 0.63, 2.3, and 13 M, respectively, vs. 620 nM using rabbit muscle 20S). A widely used inhibitor both in cultures in vitro and in animals in vivo., A cell-permeable dipeptidylboronate compound that selectively inhibits 20S proteasome beta5 ChTL/chymotrypsin- over beta1 CL/caspase- and beta2 TL/trypsin-like activity (kinact/Ki = 38,000, 5,700, and <100 M-1s-1, respectively, in human 20S proteasome assays using 10 M Suc-LLVY-AMC/Cat. No. 539142, 10 M Z-LLE-AMC/Cat. No. 539141, or 50 M Boc-LRR-AMC as substrate, IC50 in 1 h = 7, 74, and 4,200 nM, respectively) via a covalent, slowly reversible, interaction between the nucleophilic Thr1 hydroxy group/Thr1Ogamma of the catalytic beta subunit and the inhibitor's electrophilic boronic moiety, displaying much reduced potency against human chymotrypsin, cathepsin G, leukocyte elastase, and thrombin (Ki = 0.32, 0.63, 2.3, and 13 M, respectively, vs. 620 nM using rabbit muscle 20S). A widely used inhibitor both in cultures in vitro and in animals in vivo. Despite being the first proteasome inhibitor approved by FDA for clinical anticancer treatment, its therapeutic efficacy continues to be hampered by off-target effects and dose-limiting toxicity.