This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| E64 | |
|---|---|
| Name | E64 |
| Other names | L-trans-Epoxysuccinyl-leucylamido(4-guanidino)butane; N-[N-(L-3-trans-Carboxyoxirane-2-carbonyl)-L-leucyl]-agmatine |
| Formula | C15H27N3O6 |
| Molar mass | 357.39 g·mol⁻¹ |
| Appearance | white to off-white powder |
| CAS number | 87315-04-6 |
| Identifiers | IUPAC, SMILES, InChI |
E64
E64 is a synthetic epoxysuccinyl peptide widely used as an irreversible inhibitor of papain-family cysteine proteases in biochemical and biomedical research. Developed during studies of protease inhibitors, it has been employed across studies of lysosome function, apoptosis, autophagy, and infectious disease models involving organisms such as Plasmodium falciparum and Trypanosoma cruzi. The compound’s specificity for thiol-dependent proteases and its stability under physiological conditions made it a benchmark reagent in investigations by laboratories associated with institutions like the Max Planck Society and the National Institutes of Health.
E64 was characterized in the 1970s–1980s research era when groups at institutions such as the Biochemistry Research Centre and companies like Boehringer Mannheim sought irreversible inhibitors for cysteine proteases. It targets members of the papain superfamily including cathepsin B, cathepsin L, cathepsin S, and parasitic enzymes such as falcipain-2 and cruzain. The molecule’s epoxide warhead confers covalent modification of active-site thiols, and its peptidyl backbone imparts subfamily selectivity exploited in structural studies at facilities like the European Molecular Biology Laboratory.
Chemically, E64 contains an epoxysuccinyl electrophile linked to an amino acid-derived side chain reminiscent of leucine and an agmatine-derived guanidinium moiety. Its physicochemical profile—including moderate polarity, stability to hydrolysis, and crystalline form—permitted X-ray crystallography of inhibitor–enzyme complexes at centers such as Harvard University and University of Cambridge. Synthetic routes reported in organic chemistry literature from groups at ETH Zurich and MIT use stereoselective epoxidation of unsaturated succinic derivatives, peptide coupling chemistry, and guanidinylation steps. Variants and analogs were developed by medicinal chemistry teams at firms like GlaxoSmithKline and Pfizer to probe structure–activity relationships against targets including cathepsin K and calpain isoforms.
E64 acts as an irreversible cysteine protease inhibitor through nucleophilic attack of the active-site thiolate on the epoxide, yielding a stable covalent adduct. This mechanism has been elucidated using structures solved by researchers at Stanford University and ETH Zurich and confirmed by enzymology studies in labs at Columbia University and Johns Hopkins University. In cellular models from groups at University of Tokyo and University of California, San Francisco, E64 blocks lysosomal proteolysis mediated by cathepsin B and cathepsin L, thereby modulating pathways regulated by proteolytic processing such as antigen presentation studied by teams at Rockefeller University and cytokine maturation examined at Imperial College London. Parasitology and infectious disease investigators at London School of Hygiene and Tropical Medicine and NIH Tropical Medicine Unit used E64 to inhibit parasite cysteine proteases, reducing replication of Leishmania and Trypanosoma species in vitro.
E64 is widely used as a biochemical tool reagent in assays run at core facilities across universities and biotechnology companies, including Broad Institute and Wellcome Trust Sanger Institute. It serves in protease profiling, activity-based probe validation, and as a control in studies of lysosomal storage diseases by groups at UCL Great Ormond Street Institute of Child Health and Mayo Clinic. Preclinical work explored E64 analogs for therapeutic applications in conditions such as muscular dystrophy and Alzheimer's disease with contributions from research teams at University of Oxford and pharmaceutical divisions of Roche. In parasitology, E64-derived leads informed drug discovery campaigns at Medicines for Malaria Venture and academic consortia targeting Chagas disease and malaria.
Toxicological assessments performed in rodent models by researchers at National Toxicology Program and academic toxicology units indicate low acute systemic toxicity at research-use doses, but potential off-target effects arise from broad inhibition of cysteine proteases implicated in physiological processes studied at Vanderbilt University and Yale University. Standard laboratory safety guidance from institutional biosafety offices recommends handling E64 as a hazardous chemical: use of personal protective equipment in accordance with procedures developed at Oak Ridge National Laboratory and waste disposal consistent with protocols at EPA-accredited facilities. In vitro, high concentrations can perturb lysosomal integrity and autophagic flux studied at Karolinska Institutet.
E64 is not an approved therapeutic agent by regulatory authorities such as the Food and Drug Administration or the European Medicines Agency but is commercially available as a research reagent from suppliers like Sigma-Aldrich and Cayman Chemical. Material safety data and supply chain distribution are managed by vendors and institutional procurement offices at entities such as Howard Hughes Medical Institute and university purchasing departments. Researchers must comply with institutional review and chemical control policies at organizations like NIH and adhere to import/export regulations enforced by agencies such as Customs and Border Protection.
Category:Protease inhibitors