Consider the following enzymes of glycolytic pathway
1. Glyceraldehyde-3 phosphate dehydrogenase
2. Enolase
3. Pyruvate kinase
4. Phosphoglycerate kinase
The correct order in which they appear in the pathway is

Options

A. 2,1,4,3
B. 3, 2, 1, 4
C. 4, 3, 2, 1
D. 1,4,2, 3

Answer

To determine the correct order of the enzymes in the glycolytic pathway from the given options, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Enzymes and Their Functions**:
- Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
- Phosphoglycerate kinase (PGK)
- Enolase
- Pyruvate kinase (PK)

2. **Understand the Glycolytic Pathway**:
Glycolysis consists of two phases: the preparatory phase and the payoff phase. The enzymes listed are part of the payoff phase.

3. **List the Reactions in the Payoff Phase**:
- The payoff phase starts with glyceraldehyde-3-phosphate (G3P).
- The first reaction involves G3P being converted to 1,3-bisphosphoglycerate (1,3-BPG) by the enzyme **Glyceraldehyde-3-phosphate dehydrogenase**.
- The second reaction converts 1,3-BPG to 3-phosphoglycerate (3-PG) using **Phosphoglycerate kinase**.
- The third reaction converts 3-PG to 2-phosphoglycerate (2-PG) using **Phosphoglyceromutase** (not listed in the options).
- The fourth reaction converts 2-PG to phosphoenolpyruvate (PEP) using **Enolase**.
- The fifth reaction converts PEP to pyruvate using **Pyruvate kinase**.

4. **Establish the Order of Enzymes**:
Based on the reactions:
- 1. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
- 2. Phosphoglycerate kinase (PGK)
- 3. Enolase
- 4. Pyruvate kinase (PK)

5. **Final Order**:
The correct order in which the enzymes appear in the glycolytic pathway is:
- Glyceraldehyde-3-phosphate dehydrogenase (1)
- Phosphoglycerate kinase (4)
- Enolase (2)
- Pyruvate kinase (3)

Thus, the correct order is **1, 4, 2, 3**.