Neuron-specific enolase is a clinically useful tumour marker in small cell lung carcinoma and neuroblastoma. The isoenzymatic composition of this marker is:

• A Gamma-gamma homodimer ✓
• B Alpha-alpha homodimer
• C Alpha-beta heterodimer
• D Beta-beta homodimer

Explanation

Enolase is a dimeric glycolytic enzyme with three distinct subunits: alpha (ubiquitous), beta (muscle) and gamma (neuronal and neuroendocrine tissue). The gamma-gamma dimer constitutes neuron-specific enolase, released into serum by small cell lung cancer, neuroblastoma and other neuroendocrine tumours. Option D corresponds to the muscle-specific form seen in muscle injury, and option B represents the ubiquitous isoenzyme present in nearly every tissue, which is precisely why it lacks tumour specificity.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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