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Michaelis-Menten Method; Effect of pH on Enzyme

Phosphofructokinase is an enzyme, widespread in nature, catalyzing the reaction:

fructose-6-phosphate + ATP ----> fructose-1,6-diphospohate + ADP

Under conditions where the concentration of ATP was held constant, the dependency of the initial velocity of the concentration of fructose-6-phosphate as measured at two different pH values (6.9 and 8.2) is represented by the data attached. Plot the data according to the classical Michaelis-Menten method and interpret what effect the pH has on the activity of the enzyme.

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Solution Preview

Plotting the substrate concentration against the rate of the reaction gives strikingly different curves at pH 6.9 and pH 8.2. See attached file.

At pH 8.2 the reaction is classically Michaelis-Menten, with a Km 0.0425 mM and a vmax of 109 umoles/min. The maximum slope of this type of graph is at a substrate concentration of zero.

At pH 6.9 the ...

Solution Summary

Solution includes plotting the substrate concentration against the rate of the reaction in an attached Excel file and an explanation. 225 words.