What is the turnover number of an enzyme?

Explanation

**Step-by-Step Solution:**

1. **Definition of Turnover Number**: The turnover number of an enzyme is defined as the maximum number of substrate molecules that can be converted into product by a single active site of the enzyme per unit time.

2. **Active Site Consideration**: This measurement specifically pertains to a single active site of the enzyme. If an enzyme has multiple active sites, the turnover number will refer to the activity of one of those sites.

3. **Saturation Condition**: The turnover number is determined when the enzyme is saturated with substrate. This means that all active sites of the enzyme are occupied by substrate molecules, allowing for the maximum conversion rate.

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