Question 25:
Enzymes that play two distinct roles, at least one of which is catalytic, the other may be catalytic, regulatory, or structural, are called:
Moonlighting enzymes are proteins that perform multiple independent functions, including at least one catalytic role alongside others like regulation or structure. The correct answer to Question 25 is (A) Moonlighting.
Correct Answer
Option (A) Moonlighting is right. These enzymes exhibit protein moonlighting, where a single protein performs two or more unrelated functions—one catalytic (speeding reactions) and others like regulatory (e.g., signal transduction), structural (e.g., assembly), or additional catalytic roles. Examples include glycolytic enzymes like GAPDH, which also binds RNA for gene regulation.
Option Explanations
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(A) Moonlighting: Describes enzymes with multifunctionality beyond single catalysis, often evolutionarily conserved in pathways like glycolysis or TCA cycle. At least one role is catalytic; others are non-enzymatic.
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(B) Mutases: Isomerases that catalyze intramolecular group transfers, shifting functional groups within a molecule (e.g., phosphoglycerate mutase in glycolysis). They have one primary catalytic role, not dual distinct functions.
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(C) Polymerases: Enzymes (e.g., DNA/RNA polymerases) that synthesize nucleic acid chains by linking nucleotides. Strictly catalytic for polymerization, without defined secondary regulatory/structural roles.
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(D) Paralogs: Duplicate genes within a genome that evolve new functions via divergence. They are genes/proteins, not specifically enzymes with dual roles; moonlighting refers to single-protein multifunctionality.
| Option | Definition | Key Role | Matches Query? |
|---|---|---|---|
| Moonlighting | Multi-function protein (catalytic + other) | Dual roles | Yes |
| Mutases | Intramolecular transfer | Single catalysis | No |
| Polymerases | Nucleic acid synthesis | Polymerization | No |
| Paralogs | Gene duplicates | Evolutionary divergence | No |
