A reaction catalysed by an enzyme not found in mitochondiral matrix

Options

A. Conversion of pyruvic acid to acetyl CoA
B. Oxidative decarboxylation of `alpha`-ketoglutaric acid
C. Oxidation of succinic acid
D. Cleavage of succinyl CoA.

Answer

To determine which reaction is catalyzed by an enzyme not found in the mitochondrial matrix, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Context**:
- The question asks for a reaction catalyzed by an enzyme that is not located in the mitochondrial matrix. The mitochondrial structure includes the outer membrane, inner membrane, intermembrane space, and the matrix itself.

2. **Analyzing Each Option**:
- **Option 1: Conversion of Pyruvic Acid to Acetyl Coenzyme A**:
- This reaction is catalyzed by the enzyme pyruvate dehydrogenase complex, which is located in the mitochondrial matrix. Therefore, this option is incorrect.

- **Option 2: Oxidative Decarboxylation of Alpha-Ketoglutaric Acid**:
- This reaction involves converting α-ketoglutaric acid to succinyl coenzyme A, catalyzed by α-ketoglutarate dehydrogenase, which is also found in the mitochondrial matrix. Hence, this option is incorrect.

- **Option 3: Oxidation of Succinic Acid**:
- The enzyme involved here is succinate dehydrogenase, which catalyzes the conversion of succinic acid to fumarate. Importantly, succinate dehydrogenase is embedded in the inner mitochondrial membrane, not in the matrix. Thus, this option is correct.

- **Option 4: Cleavage of Succinyl Coenzyme A**:
- This reaction is facilitated by succinyl coenzyme A synthetase, which is present in the mitochondrial matrix. Therefore, this option is incorrect.

3. **Conclusion**:
- The only reaction that is catalyzed by an enzyme not found in the mitochondrial matrix is the oxidation of succinic acid, which is facilitated by succinate dehydrogenase located in the inner mitochondrial membrane.

### Final Answer:
The correct answer is **Option 3: Oxidation of Succinic Acid**.

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