Statistical Calculations of the Accuracy of the Michaelis Constant from Viscosimetric Determinations of Polymetaphosphatase and Dextranase Activity.

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Abstract
Values for Michaelis'' constant obtained with different preparations of polymeric homologous substrates can be compared by standard statistical methods if the accuracy is known, but the most common procedures for the calculation of Michaelis'' constant are not suitable for statistical accuracy calculations according to the method of least squares; however, Hanes'' equation [S]/v = Km/V + (1/V)-[S] is suitable. The use of this equation for accuracy calculations is exemplified. For Aspergillus niger polymetaphosphatase the values of Michaelis'' constant showed no significant difference for 3 preparations of polymetaphosphate, whereas a 4th preparation with a larger fraction of low molecular weight substance gave a deviating result. The 80% confidence interval for the weighted mean value of the Michaelis'' constant for the 3 preparations was 0.06-0.13% at 25[degree]C and pH 5.4 in acetate buffer of the ionic strength 0.3. For Cellvibrio fulva dextranase the 95% confidence interval for a determination of the Michaelis'' constant was 0.1-0.6% at 25[degree]C and pH 5.22; the 50% confidence interval was 0.31-0.40%.