Is a ribozyme a protein enzyme?

• A. Sometimes
• B. No
• C. Yes
• D. Only in bacteria

Answer: (B)

Ribozymes are RNA molecules that act as enzymes. Enzymes are usually proteins, but RNA can fold into precise three-dimensional shapes that create an active site and catalyze chemical reactions, using the RNA itself and sometimes bound metal ions as the catalytic tool. This means the catalytic activity comes from the RNA, not a protein. Classic examples include self-splicing introns and RNase P RNA, and the ribosome’s active center is RNA as well, underscoring RNA’s capability to carry out catalysis in biology. Some complexes include proteins to assist folding or stability, but the essential catalytic function in ribozymes is the RNA component. So, a ribozyme is not a protein enzyme.