Researchers often encounter the need to protect proteins (including phosphoproteins) from degradation during and after cell lysis and tissue protein extraction. This need often includes the preservation of the phosphorylation state (activation state) of the proteins, especially when it is that particular characteristic that is being investigated.
Phosphoprotein activation states can act as on/off switches for key cell functions like signal transduction, cell division, cell death, and calcium signaling. In order to study these types of factors, endogenous enzymes called phosphatases must be inactivated to prevent their uncontrolled activity after cell lysis. Threats to the phosphorylation state are posed by serine/threonine phosphatases as well as by protein tyrosine phosphatases (PTPs).
Sigma-Aldrich formulations of phosphatase and phosphorylase inhibitors provide protection from dephosphorylation by blocking or inactivating the endogenous enzymes that are released during cells lysis. These enzymes would otherwise affect the proteins of interest and their activation states.