Detection of the single-chain precursor in the production and purification process of recombinant human insulin.

High quality recombinant insulin requires being free of single-chain precursor (proinsulin), a task that depends on the selectivity and sensitivity of the monitoring process for detecting proinsulin. In this study we developed an enzyme-linked immunosorbent assay (ELISA) system that was specifically tailored to detect recombinant proinsulin. The proinsulin consists of six components: an initiating methionine, 48 amino acids from human growth hormones (HGH, used as the protection peptide), first connecting Arg-residue, B-chain of insulin, and second connecting Arg-peptide and A-chain of insulin. This form of proinsulin is more stable and can be efficiently expressed by E. coli than insulin. Herein, we evaluated the specificity, precision, recovery, sensitivity, and detection range of the proinsulin ELISA kit. The results showed that the ELISA kit is a very useful tool for monitoring the proinsulin yield in early stages of insulin production as well as the residual proinsulin in the final product, insulin.