Structure of hamster insulin: comparison with a tumor insulin

Insulin, isolated from hamster pancreata by acid ethanol extraction, membrane ultrafiltration, DEAE cellulose and Sephadex G50 chromatography, was pure and used for sequence studies. Amino acid sequence was established by tryptic cleavage and both manual and automatic Edman degradation. The proposed B chain sequence is identical with that of rabbit insulin, while A chain is identical to that of rat. However, this specific combination of A and B chains is unique. An insulin immunoreactive peptide was isolated from a transplantable hamster pancreatic carcinoma by a similar process. Chromatographic behavior was identical to that of normal hamster insulin but the tumor preparation was contaminated with peptides which were only removed after sulfitolysis of the tumor insulin to respective A and B chains. Amino acid composition and partial sequence data show that the tumor product is identical to the normal pancreatic insulin.