Final answer:
Repressible enzymes have their synthesis halted in the presence of certain molecules, while inducible enzymes are synthesized only when their substrate is present. Allosteric effectors and other regulators such as activators and inhibitors dynamically modulate enzyme activity and metabolism.
Step-by-step explanation:
Types of Metabolic Enzymes: Repressible and Inducible
In the regulation of enzyme synthesis, there are two main types of enzymes based on their response to the presence or absence of substances: repressible and inducible enzymes. Repressible enzymes are those whose synthesis is decreased or stopped (repressed) in the presence of certain molecules. An example of this is the trp operon, which when tryptophan is abundant, decreases the production of enzymes responsible for its synthesis. Inducible enzymes, on the other hand, are produced only when a certain substrate is present which induces their synthesis. An example is the lac operon in E. coli, which produces enzymes to metabolize lactose only when lactose is present.
Furthermore, enzyme regulation is crucial for overall metabolism control. Factors such as allosteric effectors can increase or decrease the activity of allosterically regulated enzymes, thereby modulating a metabolic pathway. Moreover, differential enzyme regulation involving activators and inhibitors can accelerate or decelerate enzyme catalysis, thereby shaping the metabolic processes in line with the cell's needs.