Sodium orthovanadate is a broad-spectrum competitive inhibitor of protein tyrosine phosphatases (PTPases) and acid and alkaline phosphatases. It is also known to inhibit ATPases. Sodium orthovanadate is soluble in water (20mg/ml) and a typical working concentration used is 1 to 100 mM. This phosphatase inhibitor can be combined with lysis and extraction buffers to support downstream purification procedures.