Name the enzyme which changes its characteristics with change in concentration of `O_2`

Options

A. PEP - Carboxylase
B. Hexokinase
C. Rubis - co
D. Pyruvic dehydrogenase

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for an enzyme that changes its characteristics with varying concentrations of oxygen (O2).

2. **Identifying the Enzymes**: The options provided are:
- Pep carboxylase
- Hexokinase
- Rubisco
- Pyruvic dehydrogenase

3. **Analyzing Each Enzyme**:
- **Pep Carboxylase**: This enzyme primarily functions in the fixation of carbon dioxide and is not directly influenced by oxygen concentration.
- **Hexokinase**: This enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate. It is known to exhibit allosteric regulation and can be inhibited by its product, glucose-6-phosphate.
- **Rubisco**: This enzyme is involved in the first major step of carbon fixation in photosynthesis. It is affected by oxygen concentration but does not change its characteristics in the same way as hexokinase.
- **Pyruvic Dehydrogenase**: This enzyme converts pyruvate into acetyl-CoA and is not primarily influenced by oxygen concentration.

4. **Focusing on Hexokinase**: Hexokinase is the enzyme that changes its characteristics due to the accumulation of glucose-6-phosphate, which leads to its inhibition. This change is a form of allosteric regulation, where the enzyme's activity is modified based on the concentration of its substrate or product.

5. **Conclusion**: The enzyme that changes its characteristics with the change in the concentration of O2 is **Hexokinase**.

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