Crude cell extracts contain a number of endogenous enzymes, such as proteases and phosphatases, which are capable of digesting the proteins present in the extract. An optimized method to improve the yield of native proteins is to add inhibitors of these enzymes known to be present in the source material. 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. T
he cocktail functions to inhibit proteases that would degrade either phosphorylated or non-phosphorylated protein substrates. TOOLS Protease Inhibitor is a blend of 5 pan-protease inhibitors for protection of protein integrity.
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 actsagainst cystein proteases. Leupeptin acts against both serine and cystein proteases.