Which one of the following statements is incorrect about enzyme catalysis ?

Options

A. Enzymes are denaturated by ultraviolet rays and at high temperature
B. Enzymes are least reactive at optimum temperature
C. Enzymes are mostly proteinous in nature
D. Enzyme action is specific

Answer

To determine which statement about enzyme catalysis is incorrect, we need to evaluate each statement provided in the question. Here’s a step-by-step analysis:

### Step 1: Understand Enzyme Denaturation
- **Statement**: Enzymes are denatured by ultraviolet rays and high temperature.
- **Analysis**: This statement is true. Enzymes can lose their functional shape (denature) when exposed to extreme conditions such as high temperatures and ultraviolet radiation.

### Step 2: Evaluate Enzyme Reactivity at Optimum Temperature
- **Statement**: Enzymes are least reactive at optimum temperature.
- **Analysis**: This statement is incorrect. Enzymes are most reactive at their optimum temperature. The optimum temperature is the temperature at which an enzyme's activity is maximized.

### Step 3: Assess the Proteinaceous Nature of Enzymes
- **Statement**: Enzymes are most proteinaceous in nature.
- **Analysis**: This statement is true. Enzymes are primarily made of proteins, which are essential for their catalytic functions.

### Step 4: Consider the Specificity of Enzymes
- **Statement**: Enzyme action is specific.
- **Analysis**: This statement is true. Enzymes are specific to their substrates, following the lock-and-key model, where only a specific substrate fits into the enzyme's active site.

### Conclusion
After evaluating all the statements, the incorrect statement is:
- **"Enzymes are least reactive at optimum temperature."**

### Final Answer
The incorrect statement about enzyme catalysis is: **"Enzymes are least reactive at optimum temperature."**

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