Proinsulin undergoes maturation into active insulin through the action of cellular endopeptidases known as prohormone convertases ( PC1 and PC2 ), as well as the exoprotease carboxypeptidase E .  The endopeptidases cleave at 2 positions, releasing a fragment called the C-peptide , and leaving 2 peptide chains, the B- and A- chains, linked by 2 disulfide bonds. The cleavage sites are each located after a pair of basic residues (lysine-64 and arginine-65, and arginine-31 and −32). After cleavage of the C-peptide, these 2 pairs of basic residues are removed by the carboxypeptidase.  The C-peptide is the central portion of proinsulin, and the primary sequence of proinsulin goes in the order "B-C-A" (the B and A chains were identified on the basis of mass and the C-peptide was discovered later).
Magnesium is common in diabetes patients. Magnesium may
help oxidizing blood glucose and increase insulin emission as various clinical
studies have reported a
decrease in fasting blood sugar level and increase in insulin after
Vanadium is a trace element that could be an alternative treatment for diabetes as it may help oxidizing blood glucose. Several clinical studies of vanadium have shown decrease in insulin intake and a positive changes in insulin sensitivity with minor side effect in the stomach and intestines.
Deficiency of Vitamin C is common in diabetes patients. Studies have shown that Vitamin C help to improve insulin resistance and glycemic control.