Final answer:
When an allosterically modulated enzyme is the rate-limited enzyme in a metabolic pathway, the entire pathway may be upregulated or downregulated by feedback inhibition.
Step-by-step explanation:
When an allosterically modulated enzyme is the rate-limited enzyme in a metabolic pathway, the entire pathway may be upregulated or downregulated by feedback inhibition.
Feedback inhibition occurs when the products of a metabolic pathway serve as inhibitors (usually allosteric) of one or more enzymes involved in the pathway. In the case of an allosterically modulated enzyme being rate-limited, an accumulation of the pathway product can bind to the enzyme and cause an allosteric change that inhibits catalysis and slows down the entire pathway.