Department of Biochemistry, Aichi Medical University School of Medicine, Nagakute, Aichi, Japan.
J Enzyme Inhib Med Chem. 2009 Dec;24(6):1288-90. doi: 10.3109/14756360902829766.
A new simple graphical method is described for the determination of inhibition type and inhibition constants of an enzyme reaction without any replot. The method consists of plotting experimental data as (V-v)/v versus the inhibitor concentration at two or more concentrations of substrate, where V and v represent the maximal velocity and the velocity in the absence and presence of inhibitor with given concentrations of the substrate, respectively. Competitive inhibition gives straight lines that converge on the abscissa at a point where [I] = -K(i). Uncompetitive inhibition gives parallel lines with the slope of 1/K'(i). For mixed type inhibition, the intersection in the plot is given by [I] = -K(i) and (V-v)/v = -K(i)/K'(i) in the third quadrant, and in the special case where K(i) = K'(i) (noncompetitive inhibition) the intersections occur at the point where [I] = -K(i) and (V-v)/v = -1. The present method, the "quotient velocity plot," provides a simple way of determining the inhibition constants of all types of inhibitors.
描述了一种新的简单图形方法，用于在无需任何重新绘图的情况下确定酶反应的抑制类型和抑制常数。该方法包括将实验数据绘制为(V-v)/v 与抑制剂浓度的关系，其中 V 和 v 分别表示在给定底物浓度下无抑制剂和有抑制剂时的最大速度和速度。竞争性抑制给出在 [I] = -K(i) 处收敛于横坐标的直线。非竞争性抑制给出斜率为 1/K'(i) 的平行线。对于混合抑制类型，在第三象限中，在图中的交点处 [I] = -K(i) 和 (V-v)/v = -K(i)/K'(i)，在特殊情况下 K(i) = K'(i)（非竞争性抑制），交点出现在 [I] = -K(i) 和 (V-v)/v = -1 的点处。这种新的“商速度图”方法提供了一种简单的方法来确定所有类型抑制剂的抑制常数。
