Preparation Note
Pepstatin can be dissolved at 1 mg/ml in 10% (v/v) acetic acid in methanol (9:1 methanol:acetic acid). The inclusion of acetic acid may be necessary to dissolve this peptide in methanol or DMSO. It has been dissolved at 1 to 2 mg/ml in ethanol, but heat may be required for complete dissolution. Solutions of Pepstatin A can be heated as high as 60 °C without any decomposition of the peptide. Stock solutions at 1 mg/ml are stable at least a week at 4 °C. A 1 mM solution in methanol or DMSO is stable for months at -20 °C. If solutions become darker yellow, the reagent is hydrolyzing.A working concentration of 1 μM is stable for at least one day at room temperature.
Biochem/physiol Actions
Pepstatin A is an inhibitor of acid proteases (aspartyl peptidases). It forms a 1:1 complex with proteases such as pepsin, renin, cathepsin D, bovine chymosin, and protease B (Aspergillus niger). The inhibitor is highly selective and does not inhibit thiol proteases, neutral proteases, or serine proteases. Solubilized γ-secretase and retroviral protease are also inhibited by Pepstatin A. It has been used to characterize proteases from several sources.