Residual Analysis in Determining the Error Structure in Enzyme Kinetic Data

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Abstract
The nature of the experimental error in the initial velocities of an enzyme-catalyzed reaction is required if meaningful least-squares regression is to be applied. When a rate equation more complex than that of Michaelis and Menten is to be solved least-squares techniques are the method of choice and so determination of the error structure becomes mandatory. The use of residual analysis and Tukey''s T statistics to determine the weights to use are described. This method has the advantage of requiring no additional experimentation over that required for the primary investigation. Using data obtained for C. maenas phosphofructokinase the variance was found to increase with velocity and was approximated by either an empirical power function, var (vi) .alpha. .**GRAPHIC**. or by the function, var (vi).alpha. 0.007 + .**GRAPHIC**. The latter function is preferred and suggests that the data contain both a constant absolute error and a constant percentage error component.