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 inhibitors of those enzymes known to be present.

Protease inhibitor cocktail is used in cell lysates or tissue extracts to increase protein stability. The cocktail functions to inhibit proteases that would degrade either phosphorylated or non-phosphorylated protein substrates.

Protease inhibitor cocktail has been optimized and tested for mammalian cell and tissue extracts. It contains inhibitors with a broad specificity for serine, cysteine, and acid proteases, and aminopeptidases. This cocktail is supplied as a ready-to-use solution in DMSO.