We have been using a cocktail of protease and phosphatase inhibitors from Cell Signalling Technology without any noticeable problems. The cocktail is 100X and ready-to-go.

Pierce Halt products have worked like a charm

HI collegue,

Protease and phosphatase inhibitors are essential components of most cell lysis and protein extraction procedures. These inhibitors block or inactivate endogenous proteolytic and phospholytic enzymes that are released from subcellular compartments during cells lysis and would otherwise degrade proteins of interest and their activation states.

Protease inhibitors are biological or chemical compounds that function by reversibly or irreversibly binding to the protease. Most known proteases belong to one of four evolutionarily distinct enzyme families based on the functional groups involved in cleavage of the peptide bond. Known phosphatases are specific for cleavage of either serine-threonine or tyrosine phosphate groups. Thus, while numerous compounds have been identified and used to inactivate or block these enzymes, no single chemical is effective for all types of proteases and phosphatases .

Rather, most researchers prepare or use a mixture or "cocktail" of several different inhibitor compounds to ensure that protein extracts do not degrade before analysis for targets of interest. Proteases inhibitors are nearly always needed, while phosphatase inhibitors are required only when phosphorylation states (activation states) are being investigated. Particular research experiments may necessitate the use of single inhibitors or customized mixtures, but most protein work is best served by using a suitable protease inhibitor cocktail .