Hormonal and Immunological Properties of Insulin Fragments: I. The Individual Peptide Chains

Abstract

Hormonal and immunological properties of the 2 polypeptide chains of beef insulin were compared with those of the parent molecule. The identity and integrity of the preparations was established by demonstrating regeneration of insulin activity on recombination of the separate chains. Using insulin immunoassays and bioassays the following observations were made: The isolated A chain has a weak stimulatory effect (about 1/1000 that of insulin) on glucose uptake by rat diaphragm, and to this extent is insulin-like. Immunologically it is unlike insulin, failing to interact with insulin neutralizing or reaginic antibodies. The B chain appeared to be quite inert, hormonally and immunologically, in the test systems used. We were unable to confirm that it is an antagonist to the action of insulin on muscle, either alone or in combination with albumin. (Endocrinology85: 368, 1969)