M R Waser | PubMed Health

PubMed1984

A computer program for analyzing enzyme kinetic data using graphical display and statistical analysis.

A computer program, PENNZYME (M. C. Kohn, L. E. Menten, and D. Garfinkel, Comput. Biomed. Res. 12, 461, 1979), that fits trial rate laws to enzyme and transport steady-state kinetic data by nonlinear regression has been enhanced. The new version includes a set of mnemonic commands which can be displayed in a menu at the user's option. Graphic displays of measured data and computed curves, as well as deviations between them (residual plots) have been added to aid the user in determining if a model is free of bias or systematic error. Other features include the ability to display the variance-covariance matrix of the parameters, to hold individual parameters constant during an optimization, and to optimize error models for the experimental data by the extended-least-squares technique.

Computers↗

PubMed1983

Computer modeling of muscle phosphofructokinase kinetics.

The kinetics of the phosphofructokinase reaction were studied by computer modeling. A general random order, two-state allosteric model, of which the Monod--Wyman--Changeux model is a limiting case, was found to most accurately reproduce the experimental observations of Pettigrew & Frieden (1979 a,b). A simplified model with Hill coefficients was found to fit almost as well. In these models substrates bind preferentially to and stabilize the enzyme in the R state, and ATPH3-, the inhibitory species, binds preferentially to and stabilizes the enzyme in the T state. Enzymatic activity is regulated by conversion from the R to the T state, which is effected by protonation, especially of the uncomplexed enzyme, but the experimental data are inadequate for accurate estimation of the pKa of the enzyme. Random order binding of substrates is an important cause of sigmoidal kinetics. Additional experiments that would aid in the discrimination among rival models are described.

Adenosine Triphosphate↗