Sigma-Aldrich Pepstatin A. ≥100,000 U/mg. 5 mg

Pepstatin A is suitable for use:

• in the inhibitor cocktail in fluorometric matrix metalloproteinase assay[1]
• as a protease inhibitor during homogenization of tissue[2]
• as a protease inhibitor during extraction of cells[3]
• to determine the molar concentrations of cathepsin D by titration with pepstatin A[4]
• in inhibiting cathepsin D[5]

It can be used in conjunction with E64-d and Leupeptin A to inhibit the degradation of autophagic cargo inside autophagosomes. For this application, the working concentration is typically between 1-10 μM.

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.

Potent inhibitor of acid proteases, including pepsin, renin and cathepsin D and many microbial aspartic proteases. Effective concentration 1 μM. Stable for about 1 day.

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.

1 U corresponds to the amount of inhibitor which reduces the activity of pepsin by 1 U (1 U corresponds to the amount of enzyme which increases the absorbance at 280 nm by 0.001 per minute at pH 2.0 and 37°C (Hemoglobin, Cat. No. 51290, as substrate, in an endvolume of 16 mL)); 10′000 absorbance-U as described above are equivalent to ∼1 Bergmeyer-U (when 1 pepsin-U is the amount of enzyme which hydrolyzes 1 μmol acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosin per minute at pH 2.0 and 37°C)

Strong inhibitor of acid proteases - pepsin, cathepsin D, renin[6][7][8]