A 35-year-old woman with type 1 diabetes uses a basal-bolus insulin regimen. She takes insulin glargine at bedtime and insulin lispro before meals. The rapid onset of insulin lispro compared to regular human insulin is due to which structural modification?
- A Addition of zinc to form stable hexamers
- B Reversal of proline and lysine at positions B28 and B29 preventing dimerization ✓
- C Attachment of a fatty acid side chain binding to albumin
- D Substitution of aspartic acid at B28 promoting hexamer formation
Correct answer: B. Reversal of proline and lysine at positions B28 and B29 preventing dimerization
Explanation
Insulin lispro has proline at B28 and lysine at B29 reversed compared to human insulin, which prevents dimerization and hexamer formation, allowing rapid absorption. Zinc addition would slow absorption. Fatty acid attachment describes insulin detemir. Aspartic acid at B28 describes insulin aspart, not lispro.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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