Endogenous proteins are produced and removed in a balanced state, so their cellular levels are generally stable under stable environmental conditions. However, protein production is greatly halted and degradation is enhanced when cells are studied in vitro. To prevent the degradation of proteins under such conditions, one can utilize a cocktail of small molecule inhibitors to block the action of proteases. The cocktail functions to inhibit proteases that would degrade either phosphorylated or non-phosphorylated protein substrates.  

ABIOM Protease Inhibitor Cocktail (EDTA free, 100× in DMSO) is a blend of 6 pan-protease inhibitors for protection of protein integrity. This mixture contains individual components, including AEBSF at 104 mM, Aprotinin at 80 μM, Bestatin at 4 mM, E-64 at 1.4 mM, Leupeptin at 2 mM and Pepstatin A at 1.5 mM. Each component has specific inhibitory properties. AEBSF and Aprotinin act to inhibit serine proteases, including trypsin, chymotrypsin, and plasmin amongst others. Bestatin inhibits aminpeptidases. E-64 acts against cystein proteases. Leupeptin acts against both serine and cystein proteases. Pepstatin A inhibits acid proteases.