The regulation of many biological processes and pathways is accomplished by the formation and cleavage of phos-phate esters. The phosphorylation of proteins is carefully balanced by an interplay of protein kinases and phospha-tases. To understand these pathways, a great deal of scien-tific work is currently being carried out within the pharma-ceutical industry and research institutes. An important step toward achieving this goal is to get an accurate view about general or specific phosphorylation status which requires a preservation of the phosphorylation pattern.Phosphorylated proteins can be dephosphorylated by either nonspecific phosphatases (e.g., alkaline phospha-tase) or the more specific protein phosphatases like ser-ine/threonine-specific, or tyrosine-specific phosphatases as well as dual-specific phosphatases.
Here, we report about the performance of a new phos-phatase inhibitor cocktail, called PhosSTP. PhosSTP is formulated as a ready-to-use tablet (Figure 1) since some of the phosphatase inhibitors are required in only nanomol amounts. It eliminates the time-consuming search for the right phosphatase inhibitors and the need to mix individual inhibitors. PhosSTP contains inhibitors against acid and alkaline phosphatases, serine/threonine phosphatase classes (e.g., PP1, PP2A and PP2B), tyrosine phosphatase (PTP) as well as dual-specific phosphatases.One Phosphatase Inhibitor Cocktail Tablet is used for 10 ml lysate. However, since the solubility is very good, 2 or 3 tablets can be used for the same volume if neces-sary. Alternatively, a stock solution can be used if smaller volumes are desired. This stock solution is stable for more than a month at 4°C and can be frozen at -20°C for at least 6 months.