The enzyme that catalyses carbon dioxide fixation in `C_(4)` plants is

Options

A. RuBP carboxylase (RUBISCO)
B. PEP carboxylase (PEPco)
C. Carbonic anhydrase
D. Carboxy dismutase

Answer

To answer the question regarding the enzyme that catalyzes carbon dioxide fixation in C4 plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Plants**:
- C3 and C4 plants have different mechanisms for fixing carbon dioxide during photosynthesis. C3 plants primarily use the Calvin cycle, while C4 plants have a specialized pathway.

2. **Identify the Enzymes**:
- The question provides four options:
- RUBP carboxylase (Rubisco)
- PEP carboxylase
- Carbonic anhydrase
- Carboxy dismutase

3. **Analyze Each Option**:
- **RUBP Carboxylase (Rubisco)**: This enzyme is primarily involved in the Calvin cycle in C3 plants, where it catalyzes the fixation of carbon dioxide to ribulose bisphosphate (RuBP). It is not the primary enzyme in C4 plants.
- **PEP Carboxylase**: This enzyme is crucial in C4 plants. It catalyzes the fixation of carbon dioxide to phosphoenolpyruvate (PEP), forming oxaloacetic acid, a four-carbon compound. This is the key enzyme in the C4 pathway.
- **Carbonic Anhydrase**: This enzyme facilitates the conversion of carbon dioxide and water into bicarbonate and protons. It plays a role in carbon dioxide transport but is not directly responsible for carbon fixation in C4 plants.
- **Carboxy Dismutase**: This term is less commonly used and can refer to various enzymes. However, it is not specifically associated with carbon dioxide fixation in C4 plants.

4. **Conclusion**:
- Based on the analysis, the enzyme that catalyzes carbon dioxide fixation in C4 plants is **PEP carboxylase**.

### Final Answer:
The enzyme that catalyzes carbon dioxide fixation in C4 plants is **PEP carboxylase**.

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