Endogenous proteins are produced and degraded in a balanced state, so their cellular levels are stable under stable environmental conditions. Crude cell extracts contain a number of endogenous enzymes, such as phosphatases and proteases, which are capable of degrading proteins in the extracts. Protein production is greatly halted and degradation is increased when proteins are extracted from cells and tissues in vitro. The best way to increase the yield of intact proteins is to add inhibitors of those enzymes known to be present. Protease inhibitors are tremendously valuable and useful reagents for researchers who want to inhibit general degradation of proteins in tissue or cell extracts by endogenous proteases, or to investigate particular processes that involve blocking the activity of specific proteases

Protease Inhibitor Cocktail is an universal protease inhibitor cocktail contains individual components, including AEBSF, Aprotinin, Bestatin, E-64, Leupeptin and Pepstatin A with a broad specificity for cysteine, serine, acid proteases, and aminopeptidases. This protease inhibitor cocktail has been optimized and tested for mammalian cells and tissue extracts.