Insulin lispro acts faster than regular human insulin after subcutaneous injection. The structural change responsible is:

• A Addition of two arginine residues at the C-terminus of the B chain
• B Replacement of alanine A8 with glycine
• C Inversion of proline B28 and lysine B29 in the B chain ✓
• D Deletion of the B30 terminal threonine

Explanation

Lispro reverses the order of proline C28 and lysine C29. Proline at position C28 drives self-association of insulin molecules into hexamers at the injection site; disrupting this sequence reduces hexamer formation, so monomers diffuse rapidly into the circulation and onset occurs within about 15 minutes. Two added arginines describe glargine, and deletion of C30 threonine describes insulin aspart's cousin detemir-related modifications, not lispro.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.