CHROMIUM OLIGOPEPTIDE ACTIVATES INSULIN-RECEPTOR TYROSINE KINASE-ACTIVITY

A possible new mechanism for the amplification of insulin receptor tyr osine kinase activity in response to insulin has been identified. The chromium-containing oligopeptide low molecular weight chromium-binding substance (LMWCr) does not effect the tyrosine protein kinase activit y of rat adipocytic membrane fragments in the absence of insulin; howe ver, insulin-stimulated kinase activity in the membrane fragments is i ncreased up to 8-fold by the oligopeptide. Using isolated rat insulin receptor, LMWCr has been shown to bind to insulin-activated insulin re ceptor with a dissociation constant of circa 250 pM, resulting in the increase of its tyrosine protein kinase activity. The ability of LMWCr to stimulate insulin receptor tyrosine kinase activity is dependent o n its chromium content. The results appear to explain the previously p oorly understood relationship between chromium and adult-onset diabete s and cardiovascular disease.