Patent ID: 7384760

Claim:
A method for assaying for an inhibitor of a S-adenosylmethionine (SAM)-dependent methyltransferase, comprising: a) contacting a SAM-dependent methyltransferase with (i) a substrate of the methyltransferase, (ii) SAM, and (iii) in the presence or absence of a compound suspected of being an inhibitor of the methyltransferase, under a condition that a methyl group is transferred from SAM to the substrate and SAM is converted to SAH: b) contacting the resulting SAH with a SAH hydrolase and a tracer under a condition that allows hydrolysis of the SAH into adenosine (Ado) and homocysteine (Hcy) catalyzed by the SAH hydrolase; wherein the tracer is a labeled SAH or a labeled SAH analog and is not hydrolyzed by the SAH hydrolase; wherein the SAH hydrolase is wildtype or has one or more conservative amino acid substitutions that do not substantially alter its catalytic activity, and wherein i) the tracer generates a detectable signal after binding to the SAH hydrolase, or ii) the SAH hydrolase is immobilized on a suitable surface; c) detecting binding of the tracer to the SAH hydrolase; and d) comparing the amount of binding of the tracer to the SAH hydrolase in the presence of the compound to the amount of binding in the absence of the compound, whereby an increase in the amount of binding in the presence of the compound compared to the amount of binding in the absence of the compound indicates that the compound is an inhibitor of the SAM-dependent methyltransferase.