Feedback inhibition of an enzyme is influenced by

Options

A. enzyme itself
B. external factors
C. end product
D. substrate.

Explanation

### Step-by-Step Solution:

1. **Understanding Feedback Inhibition**: Feedback inhibition is a regulatory mechanism where the accumulation of an end product of a metabolic pathway inhibits an enzyme involved in its production. This helps maintain homeostasis within the cell.

2. **Enzyme-Substrate Interaction**: Enzymes catalyze reactions by converting substrates into products. The reaction can be represented as:
\[ \text{Substrate} + \text{Enzyme} \rightleftharpoons \text{Product} \]
This indicates that the substrate can be converted into the product and vice versa.

3. **Accumulation of Product**: As the reaction proceeds, the product accumulates. When there is a significant amount of product present, it sends a feedback signal to the enzyme.

4. **Effect of Feedback Signal**: The feedback signal from the accumulated product leads to the deactivation of the enzyme. This occurs because the product can bind to the enzyme and change its active site, preventing the substrate from binding.

5. **Example of Feedback Inhibition**: A classic example is the conversion of glucose to glucose 6-phosphate by the enzyme hexokinase. When glucose 6-phosphate accumulates, it inhibits hexokinase, thereby stopping further conversion of glucose to glucose 6-phosphate.

6. **Conclusion**: Therefore, feedback inhibition of an enzyme is primarily influenced by the end product of the metabolic pathway, not by the enzyme itself, external factors, or the substrate.

### Final Answer:
Feedback inhibition of an enzyme is influenced by the **end product**.

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