Which enzyme is required for the following conversion ?
Pyruvic acid `+CoA+NAD^(+) to "Acetyl" CoA+CO_(2)+NADH+H^(+)`

Options

A. Pyruvate dehydrogenase
B. Phosphoglucomutase
C. Pyruvate oxidase
D. Pyruvate carboxylase

Answer

To determine which enzyme is required for the conversion of pyruvic acid to acetyl CoA, we need to analyze the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reaction**: The reaction in question is:
\[ \text{Pyruvic acid} + \text{CoA} + \text{NAD}^+ \rightarrow \text{Acetyl CoA} + \text{CO}_2 + \text{NADH} + \text{H}^+ \]
This reaction involves the conversion of pyruvic acid into acetyl CoA, along with the release of carbon dioxide and the production of NADH.

2. **Understand the Process**: This conversion is part of cellular respiration, specifically during the transition from glycolysis to the Krebs cycle. Pyruvic acid, which is produced from glucose during glycolysis, must be converted into acetyl CoA to enter the Krebs cycle.

3. **Recognize the Enzyme Involved**: The enzyme that catalyzes this specific reaction is known as the **pyruvate dehydrogenase complex**. This is not a single enzyme but a multi-enzyme complex that facilitates the decarboxylation of pyruvate.

4. **Components of the Enzyme Complex**: The pyruvate dehydrogenase complex consists of three main components:
- **Pyruvate Dehydrogenase**: The primary enzyme that catalyzes the conversion.
- **Dihydrolipoyl Transacetylase**: Assists in the transfer of the acetyl group.
- **Dihydrolipoyl Dehydrogenase**: Regenerates the oxidized form of lipoic acid.

5. **Conclusion**: Therefore, the enzyme required for the conversion of pyruvic acid to acetyl CoA is the **pyruvate dehydrogenase complex**. Among the options provided, the closest correct answer is **pyruvate dehydrogenase**, which refers to the main enzyme in the complex.

### Final Answer:
The enzyme required for the conversion is **pyruvate dehydrogenase** (part of the pyruvate dehydrogenase complex).