Who proposed lock and key hypothesis of enzyme activity ?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the person who proposed the lock and key hypothesis of enzyme activity.

2. **Defining the Lock and Key Hypothesis**: This hypothesis suggests that enzymes and substrates fit together like a lock and key. The enzyme (lock) has a specific shape that only allows a particular substrate (key) to fit into it, forming an enzyme-substrate complex.

3. **Identifying the Proposer**: The lock and key hypothesis was first proposed by Emil Fischer, a German biochemist.

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