Sodium orthovanadate is a commonly used general inhibitor for protein tyrosine phosphatases (PTPs), alkaline phosphatase (ALP), and ATPase. Sodium orthovanadate acts as a competitive inhibitor and is completely reversible upon the addition of EDTA or by dilution. The PTP activities are conveniently separable from the protein phosphoseryl and phosphothreonyl phosphatase (PSP) activities inhibited by fluoride and EDTA. Vanadate is routinely used to preserve the protein tyrosyl phosphorylation state in cells, cell lysates, and protein tyrosine kinase assays. Sodium orthovanadate is also an inhibitor of adenosine kinase (AK) and phosphofructokinase (PFK).