Synthesis and properties of carbonylbis(methionyl)insulin, a proinsulin analogue which is convertible to insulin by cyanogen bromide cleavage

Area of Science:

• Biochemistry
• Protein Chemistry
• Reagent Development

Background:

• Insulin's structure and function are critical for diabetes treatment.
• Developing specific reagents for protein modification is essential for biochemical research.

Purpose of the Study:

• To prepare and characterize a novel reversible cross-linking reagent for insulin.
• To evaluate the properties and activity of the cross-linked insulin derivative.
• To establish a method for efficient regeneration of active insulin from the cross-linked form.

Main Methods:

• Synthesis of carbonylbis(L-methionine p-nitrophenyl ester) reagent.
• Cross-linking of zinc insulin to form NalphaA1, NepsilonB29-carbonylbis(methionyl)insulin (CBM-insulin).
• Characterization of CBM-insulin using end group analysis, enzymatic cleavage, and circular dichroism spectroscopy.
• Reversion of CBM-insulin to active insulin using cyanogen bromide and reoxidation studies.

Main Results:

• CBM-insulin was successfully synthesized, retaining 91% immunological and 6.5% hormonal activity.
• Reversion with cyanogen bromide yielded insulin with 70-80% recovery.
• Circular dichroism studies revealed pH-dependent structural changes in reduced CBM-insulin.
• Optimal conditions for disulfide bond reoxidation yielded up to 85% correctly paired bonds.

Conclusions:

• Carbonylbis(L-methionine p-nitrophenyl ester) is an effective reversible cross-linking reagent for insulin.
• The cross-linking and subsequent cleavage methods allow for the recovery of biologically active insulin.
• This reagent and methodology offer potential applications in insulin research and modification.