Final answer:
Cells prevent simultaneous modulation of all enzymes by having specific modulators for each enzyme and by using regulatory mechanisms, such as phosphatases for dephosphorylation and phosphodiesterase for degrading cAMP, to ensure targeted and appropriate response instead of blanket modulation.
Step-by-step explanation:
Cells prevent the simultaneous modulation of all covalently modulated enzymes by utilizing different mechanisms to specifically regulate the activity of enzymes. Although phosphate may be a common modulator, each enzyme has unique regulatory mechanisms that respond to distinct sets of modulators, such as positive and negative effectors.
Furthermore, cells contain different enzymes like phosphatases and phosphodiesterase, which reverse the modifications that result from signaling cascades. Phosphatases remove phosphate groups in a process called dephosphorylation, and phosphodiesterase converts cyclic AMP (CAMP) into AMP, thus terminating the signaling. This system of checks and balances ensures that each enzyme is modulated according to the cell's specific needs and does not lead to a blanket modulation of all enzymes.
Feedforward activation or feedback inhibition is another way to regulate enzymes such as in the case of substance E binding to enzyme 1, demonstrating a common mode of allosteric regulation. Each enzyme thus has a precise control mechanism to govern its activity, preventing widespread, indiscriminate modulation.