Question

Which of the following statement regarding Cytochrome P450 enzymes is incorrect?

• A. They are involved in the production of steroids
• B. They absorb maximum light at 450 nm wavelength
• C. They are present in the endoplasmic reticulum of the liver cells
• D. They are non-heme proteins

Hint:

All cytochromes are hemoproteins, meaning they contain a heme group (iron-coordinating porphyrin ring) which is essential for their oxygen-binding and electron transfer capabilities.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Cytochrome P450 (CYP) enzymes represent a major superfamily of enzymes that catalyze the oxidation of organic substances, playing a vital role in drug metabolism and steroidogenesis.
Detailed Explanation:
Let us evaluate each of the statements:
- Option (A): CYP450 enzymes are highly involved in endogenous biochemical pathways, including the synthesis of cholesterol, steroids, and bile acids. This is correct.
- Option (B): The name "P450" is derived from the fact that these pigments exhibit an absorption maximum peak at $450 \text{ nm}$ when their reduced iron is bound to carbon monoxide. This is correct.
- Option (C): They are membrane-bound proteins located predominantly in the smooth endoplasmic reticulum of hepatocytes (liver cells), where they perform Phase I biotransformation reactions. This is correct.
- Option (D): Cytochrome P450 enzymes contain an iron-protoporphyrin IX prosthetic group.
This means they are hemoproteins (heme-containing proteins), not non-heme proteins. This is incorrect.

Step 2: Final Answer:
The incorrect statement is (D).