Isomerases catalyze intramolecular rearrangements by converting a molecule into its isomer through internal atomic repositioning.

Question Analysis

This question focuses on enzyme classification (EC system), specifically identifying which class handles intramolecular shifts without net addition/removal of groups.

Option Breakdown

• Transferases: Transfer functional groups (e.g., phosphate, methyl) from one molecule to another; intermolecular, not rearrangements within one molecule.​

• Oxidoreductases: Catalyze oxidation-reduction reactions via electron/hydride transfer; alter redox states, not structural isomerization.​

• Isomerases: Facilitate intramolecular rearrangements, converting a compound to its isomer (e.g., glucose-6-P to fructose-6-P via phosphoglucose isomerase); no atoms added/removed.

• Lyases: Cleave C-C, C-O, C-N bonds by elimination, forming double bonds or rings; add water across bonds reversibly, not pure rearrangements.​

Answer: Isomerases—specialized for internal molecular restructuring.​

Introduction to Enzyme Catalysis

Intramolecular rearrangements catalyzed by isomerases enable critical metabolic shifts, like glycolysis intermediates. These enzymes rearrange bonds within a single molecule for isomer formation.

Isomerase Mechanism

Isomerases (EC 5) use acid-base or covalent catalysis to interconvert stereoisomers, anomers, or functional group positions. Example: Triose phosphate isomerase interchanges dihydroxyacetone-P and glyceraldehyde-3-P.​

Other Enzyme Classes Compared

Transferases move groups between molecules; oxidoreductases handle redox; lyases break bonds eliminatively. None perform the internal reshuffling defining isomerases.​

Biological Relevance

In pathways like glycolysis and gluconeogenesis, intramolecular rearrangements catalyzed by isomerases ensure reversible, efficient flux—key for exam questions on enzyme function.​