Cayman’s Methyltransferase Colorimetric Assay Kit is a continuous enzyme-coupled assay that can monitor SAM-dependent methyltransferases.{15387} The assay scheme outlines the general scheme of the assay. The removal of the methyl group from SAM generates S-adenosylhomocysteine (AdoHcy), which is rapidly converted to S-ribosylhomocysteine and adenine by AdoHcy nucleosidase. This rapid conversion prevents the buildup of AdoHcy and its feedback inhibition on the methylation reaction. Finally, the adenine is converted to hypoxanthine, by adenine deaminase, which in turn is converted to urate and hydrogen peroxide (H2O2). The rate of production of H2O2 is measured with the colorimetric reagents, 3,5-dichloro-2-hydroxybenzenesulfonic acid and 4-aminoantipyrine, by an increase in absorbance at 515 nm. The assay is supplied with AdoHcy as a positive control. The assay can be used with any purified SAM-dependent methyltransferase.
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