AMPK partial purification and in vitro kinase assay
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Liver AMPK is partially purified from male SD rats to the blue-Sepharose step. The 100-μL reaction mixture contains 100 μM AMP, 100 μM ATP (0.5 μCi 33P-ATP per reaction), and 50 μM SAMS in a buffer (40 mM HEPES, pH 7.0, 80 mM NaCl, 0.8 mM EDTA, 5 mM MgCl2, 0.025% BSA, and 0.8 mM DTT). The reaction is initiated with addition of the enzyme. After 30-minute incubation at 30°C, the reaction is stopped by addition of 80 μL 1% H3PO4. Aliquots (100 μL) are transferred to 96-well MultiScreen plates. The plate is washed three times with 1% H3PO4 followed by detection in a Top-count. The in vitro AMPK inhibition data obtained with compound C-(6-[4-(2-Piperidin-1-yl-ethoxy)-phenyl)]-3-pyridin-4-yl-pyyrazolo[1,5-a] pyrimidine- are fit to the following equation for competitive inhibition by nonlinear regression using a least-squares Marquardt algorithm in a computer program written by N. Thornberry of Merck Research Laboratories: Vi/Vo = (Km + S)/[S + Km × (1 + I/Ki)], where Vi is the inhibited velocity, Vo is the initial velocity, S is the substrate (ATP) concentration, Km is the Michaelis constant for ATP, I is the inhibitor (compound C) concentration, and Ki is the dissociation constant for compound C.
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References:
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2. Yu, P. B., Hong, C. C., Sachidanandan, C., Babitt, J. L., Deng, D. Y., Hoyng, S. A., Lin, H. Y., Bloch, K. D. and Peterson, R. T. (2008) Dorsomorphin inhibits BMP signals required for embryogenesis and iron metabolism. Nat Chem Biol. 4, 33-41
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