Define turn over number. Give one example,

Explanation

### Step-by-Step Solution:

1. **Definition of Turnover Number**:
- The turnover number is defined as the maximum number of substrate molecules that an enzyme can convert into product per second. It reflects the efficiency of an enzyme in catalyzing a reaction.

2. **Representation**:
- The turnover number is often represented by the symbol \( K_{cat} \).

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