Enzyme Stereospecificity in Glucose Oxidation

Steps:

• D-glucose and L-glucose are enantiomers, mirror-image stereoisomers with identical connectivity but opposite configurations at chiral centers.
• Enzymes like glucose oxidase have chiral active sites shaped to bind only one enantiomer precisely.
• L-glucose's opposite configuration prevents it from fitting the active site, blocking catalysis.
• This specificity ensures the enzyme oxidizes only the natural D-form.

Why A is correct:

• Enzymes exhibit stereospecificity; their active sites are complementary to the precise 3D shape of the substrate enantiomer, as per the lock-and-key model.

Why the others are wrong:

• B: Enantiomers share the same structural formula (connectivity) but differ in spatial arrangement.
• C: Mirror-image status describes the relationship but does not explain the catalytic failure—fit into the active site does.
• D: Synthetic origin is irrelevant; enzyme activity depends on molecular shape, not production method.

Final answer: A