After removal of the precursor signal peptide, proinsulin is post-translationally cleaved into two chains (peptide A and peptide B) that are covalently linked via two disulfide bonds.

Binding of this mature form of insulin to the insulin receptor (INSR) stimulates glucose uptake. A variety of mutant alleles with changes in the coding region have been identified.

There is a read-through gene, INS-IGF2, which overlaps with this gene at the 5' region and with the IGF2 gene at the 3' region.