Use nonlinear regression to obtain the most accurate values of Km and Vmax. The problem is that the transformations (reciprocals) distort the experimental error, so the double-reciprocal plot does not obey the assumptions of linear regression. If you do this, you won't get the most accurate values for Vmax and Km. Don't use the slope and intercept of a linear regression line to determine values for Vmax and Km. If you create a Lineweaver-Burk plot, use it only to display your data. One way to do this is with a Lineweaver-Burk plot, which plots the reciprocal of substrate concentration vs. Create a Lineweaver-Burk plotīefore nonlinear regression was available, investigators had to transform curved data into straight lines, so they could analyze with linear regression. It is the substrate concentration needed to achieve a half-maximum enzyme velocity. Km is the Michaelis-Menten constant, in the same units as X. It is the velocity of the enzyme extrapolated to very high concentrations of substrate, so its value is almost always higher than any velocity measured in your experiment. Vmax is the maximum enzyme velocity in the same units as Y. You can also choose Prism's sample data: Enzyme kinetics - Michaelis-Menten.Īfter entering data, click Analyze, choose nonlinear regression, choose the panel of enzyme kinetics equations, and choose Michaelis-Menten enzyme kinetics.

If you have several experimental conditions, place the first into column A, the second into column B, etc. Enter substrate concentration into X, and enzyme velocity into Y. If your goal is to determine the turnover number kcat, rather than the Vmax, use an alternative version of the equation.

The goal is to determine the enzyme's Km (substrate concentration that yield a half-maximal velocity) and Vmax (maximum velocity). The most common kind of enzyme kinetics experiment is to vary the concentration of substrate and measure enzyme velocity.

Curve fitting file deltagraph 7