Assay Method Information

Assay Name:  QC Inhibition Assay
Description:  An inhibition activity assay of QC inhibitors was conducted. See Huang et al., J. Biol. Chem. 2011, 286, 12439-12449. A reaction mixture containing 300 μM of Gln-βNA and 0.2 units of human PAP I was prepared. QC was first incubated with an inhibitor at 25° C. for 30 minutes and the enzyme-inhibitor mixture was then added to the reaction mixture to initiate the cyclization reaction. An IC50 value was obtained by fitting an initial reaction rate versus an inhibitor concentration using KaleidaGraph. A Ki value of the inhibitor was calculated according to an equation IC50=Ki(1+[S]/Km). See Segel, Enzyme Kinetics: Behavior and Analysis of Rapid Equilibrium and Steady-State Enzyme Systems, pp. 100-118. New York: John Wiley & Sons, 1993. In this equation, [S] is a substrate (i.e., Gln-βNA) concentration and Km is a Michaelis-Menten constant. The lower the Ki value, the higher the inhibitor's QC inhibition rate.
Affinity data for this assay
 

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