graphpad prism 5 regression curves inhibitor

The constant I is the concentration of inhibitor, a value you enter into each column title. Be sure to enter concentrations, not logarithms of concentration.Īlternatively, choose the competitive enzyme inhibition sample data set.Īfter entering data, click Analyze, choose nonlinear regression, choose the panel of enzyme kinetics equations, and choose Competitive enzyme inhibition. Enter these concentrations into the column titles. Each data set (Y column) represents data collected in the presence of a different concentration of inhibitor, starting at zero. Enter substrate concentration into the X column, and enzyme activity into the Y columns. You can determine the Ki of a competitive inhibitor by measuring substrate-velocity curves in the presence of several concentrations of inhibitor. The Vmax doesn't change, and the effective Km increases. A competitive inhibitor reversibly binds to the same site as the substrate, so its inhibition can be entirely overcome by using a very high concentration of substrate.

Graphpad prism 5 regression curves inhibitor