Question

The major class of enzymes catalyzing the cleavage of \(C-C\), \(C-O\), \(C-N\), or other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds in any biochemical reactions is ______.

• A. lyases
• B. transferases
• C. oxidoreductases
• D. hydrolases

Hint:

Recall the six IUBMB enzyme classes and match the elimination-based bond cleavage mechanism to the correct one.

Answer 1

The Correct Option is A

Enzymes are classified into six major classes based on the type of reaction they catalyze, and this question asks which class handles cleavage of bonds through elimination rather than hydrolysis or oxidation-reduction.
Step 1: Recall the six enzyme classes. The International Union of Biochemistry groups all enzymes into oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases, each defined by a distinct reaction mechanism.
Step 2: Match the description to a class. The question describes an enzyme that cleaves \(C-C\), \(C-O\), \(C-N\), or other bonds by elimination, leaving behind double bonds or rings, or that adds groups across existing double bonds. This is precisely the defining behavior of lyases, which act without using water (unlike hydrolases) and without transferring electrons (unlike oxidoreductases).
Step 3: Eliminate the other options. Transferases move a functional group from one molecule to another; oxidoreductases catalyze electron transfer (oxidation-reduction) reactions; hydrolases break bonds specifically by adding a water molecule across the bond. None of these match the elimination-based, non-hydrolytic bond cleavage described.
Step 4: Conclude. Since the mechanism described is elimination (not hydrolysis or redox), the enzyme class is lyases, option (A).