Page 439 - Excel for Scientists and Engineers: Numerical Methods

416 EXCEL: NUMERICAL METHODS

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Figure A4-11. Michaelis-Menten enzyme kinetics.
The curve follows equation A4-9 with V,, = 50, K,, = 0.5.

Double Reciprocal Plot. The Michaelis-Menten equation can be converted
to a straight line equation by taking the reciprocals of each side. This treatment
is called a Lineweaver-Burk plot, a plot of the reciprocal of the enzymatic
reaction velocity (UV) versus the reciprocal of the substrate concentration
(l/[SI).

1 K,1 1
- +- (A4- 10)
V Vmax S Vmax
A double-reciprocal plot of the data of Figure A4-11 is shown in Figure A4-
12. The parameters V,,, and K,,, can be obtained from the slope and intercept of
the straight line (Vmm = Uintercept, K,,, = interceptlslope). However,
relationships dealing with the propagation of error must be used to calculate the
standard deviations of V,,, and K, from the standard deviations of slope and
intercept. By contrast, when the Solver is used the expression does not need to
be rearranged, ycalc is calculated directly from equation A4-19, the Solver returns
the coefficients V,,, and K,,,, and SolvStat.xls returns the standard deviations of
V,,, and K,.