Which class of enzymes is primarily responsible for adding hydroxyl groups to compounds?

• A. Hydrolases
• B. Transferases
• C. Ligases
• D. Oxidoreductases

Answer: (D)

The class of enzymes primarily responsible for adding hydroxyl groups to compounds is oxidoreductases. This class of enzymes catalyzes oxidation-reduction reactions, where they facilitate the transfer of electrons between substrates. In many cases, these reactions involve the addition of hydroxyl groups to various organic molecules, particularly during metabolic processes such as hydroxylation, where an -OH group is introduced onto a substrate.

Oxidoreductases play a crucial role in various biochemical pathways, including those that modify the structures of steroids, phenols, and other compounds, ultimately affecting their solubility and reactivity. This addition of hydroxyl groups is important for the bioactivation or deactivation of drugs and other biochemical substances.

In contrast, hydrolases are enzymes that catalyze the cleavage of bonds through the addition of water, typically breaking down larger molecules into smaller ones. Transferases are responsible for transferring functional groups (not specifically hydroxyls) from one molecule to another without the addition of water. Ligases function to join two molecules together, typically utilizing the energy derived from ATP hydrolysis to facilitate the process. Thus, the distinctive role of oxidoreductases in mediating hydroxyl group incorporation makes them the correct choice for this question.