Patent ID: 7674600

Claim:
A method of screening for a substance that modulates the activity of an enzyme that can catalyze a phosphate modification on a substrate to form a product, said method comprising the steps of i) contacting the substrate and enzyme in the presence or absence of the substance and in the presence of indium (III) ion or zirconium (IV) ion, wherein the indium (III) ion or zirconium (IV) ion can bind to either the substrate or the product but not to both; ii) measuring the extent of binding between the indium (III) ion or ziroconiuin (IV) ion and the substrate or the product in the presence or absence of the substance; and iii) determining the difference in the extent of binding in step ii) between when the substance is present and when the substance is absent which correlates with the substance modulating the activity of the enzyme; wherein the enzyme is selected from the group consisting of kinases, phosphatases, cyclases and phosphodiesterases.