INS, also known as insulin preproprotein, is a biologically inactive precursor to the biologically active endocrine hormone insulin. Insulin is an essential hormone for maintaining metabolic homeostasis in the body. To make fully bioactive insulin, pancreatic beta cells initiate synthesis of INS. It is converted into proinsulin by signal peptidases, which remove its signal peptide from its N-terminus. Finally, proinsulin is converted into the bioactive hormone insulin by removal of the C-peptide. Recombinant human INS, fused to His-tag at N-terminus, was expressed in E.coli and purified by conventional chromatography techniques. MW: 11.8 kDa (109 aa), confirmed by MALDI-TOF. Purity ≥ 95%