Which of the following is an example of isozyme ?

Options

A. `alpha`-amylase
B. Glucokinase
C. Lactate dehydrogenases
D. All of these

Explanation

To determine which of the following is an example of an isozyme, we need to understand the definition of isozymes and analyze the options provided: alpha amylase, glucokinase, lactate dehydrogenase, or all of these.

### Step-by-Step Solution:

1. **Understand the Definition of Isozymes**:
- Isozymes are different forms of an enzyme that catalyze the same reaction but differ in structure and kinetic properties. They can be produced in different tissues or at different developmental stages.

2. **Analyze Each Option**:
- **Glucokinase**: This enzyme is an isozyme of hexokinase. It plays a role in glucose metabolism and is not inhibited by glucose 6-phosphate, making it an example of an isozyme.
- **Alpha Amylase**: This enzyme is found in the endosperm of wheat and has multiple isoforms (16 isozymes). It is involved in starch digestion, confirming that it is also an isozyme.
- **Lactate Dehydrogenase**: This enzyme exists as a tetramer composed of different subunits, resulting in five different isozymes. It catalyzes the conversion of lactate to pyruvate and vice versa.

3. **Conclusion**:
- Since all three options (glucokinase, alpha amylase, and lactate dehydrogenase) are examples of isozymes, the correct answer is **all of these**.

### Final Answer:
All of these (alpha amylase, glucokinase, lactate dehydrogenase) are examples of isozymes.

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