Answer to Question #83730 in Biochemistry for Duku Emmanuel
phosphate to form fructose 1,6-bisphosphate and ADP and discovered that a plot of the
initial velocity of formation of fructose 1,6-bisphosphate versus ATP concentration was
not hyperbolic, but rather sigmoid, what would you suspect?
Sigmoidal shape of the enzyme activity plot demonstrates the presence of cooperativity. It means that the enzyme consists of several subunits that act as regulators of each other. Moreover, if a sigmoid curve has a decline, it can be suggested that ATP acts as a negative allosteric regulator (inhibitor) of the enzyme. As a result, at low ATP concentrations, enzyme activity increases gradually to a certain maximal level whereas high ATP concentrations inhibit the enzyme.