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Catalog No. E3132 Name Sigma Aldrich
CAS Number 66701-25-5 Website http://www.sigmaaldrich.com
M. F. C15H27N5O5 Telephone 1-800-521-8956
M. W. 357.40538 Fax
Purity Email
Storage Chembase ID: 132401


IUPAC name
(2R,3R)-3-{[(1S)-1-[(4-carbamimidamidobutyl)carbamoyl]-3-methylbutyl]carbamoyl}oxirane-2-carboxylic acid
IUPAC Traditional name
(2R,3R)-3-{[(1S)-1-[(4-carbamimidamidobutyl)carbamoyl]-3-methylbutyl]carbamoyl}oxirane-2-carboxylic acid
N-(trans-Epoxysuccinyl)-L-leucine 4-guanidinobutylamide


MDL Number MFCD00080261
PubChem SID 24278411
Beilstein Number 1405664
CAS Number 66701-25-5


Personal Protective Equipment Eyeshields, Gloves, type N95 (US), type P1 (EN143) respirator filter
RTECS RR0390000
Storage Temperature 2-8°C
German water hazard class 3
Solubility H2O: soluble1 mM (Stock Solutions stable for months at –20° C.)


Description (English)
Preparation Note
E-64 is soluble in water. A 20 mg/ml solution can be prepared in water (heat may be needed). A suggested stock solution is a 1 mM aqueous solution. The effective concentration for use as a protease inhibitor is 1 to10 μM. Aqueous stock solutions are stable for months at -20 °C. Diluted solutions are stable for days at neutral pH. E-64 is stable from pH 2-10, but is unstable in ammonia or in HCl. E-64 is also soluble in DMSO, a 10 mM solution can be prepared in dry DMSO and stored at -20 °C. Subsequent dilutions were in culture medium. Solutions for injection were prepared by dissolving E-64 in 0.9% sodium chloride or in a minimum amount of saturated sodium bicarbonate followed by dilution with 0.9% sodium chloride (after adjusting the pH to 7.0 with acetic acid).
E-64 is an effective ligand for affinity purification of cysteine proteases. When coupled to a thiolated affinity matrix, binding is no longer irreversible, but specificity is retained.1
Biochem/physiol Actions
E-64 is an irreversible, potent, and highly selective cysteine protease inhibitor. E-64 does not react with the functional thiol group of non-protease enzymes, such as L-lactate dehydrogenase or creatine kinase. E-64 will not inhibit serine proteases (except trypsin) like other cysteine protease inhibitors, leupeptin and antipain. The trans-epoxysuccinyl group (active moiety) of E-64 irreversibly binds to an active thiol group in many cysteine proteases, such as papain, actinidase, and cathepsins B, H, and L to form a thioether linkage. E-64 is a very useful cysteine protease inhibitor for use in in vivo studies because it has a specific inhibition, it is permeable in cells and tissues and has low toxicity.