Receptor binding and biological activity of [SerB24]-insulin, an abnormal mutant insulin

SerB24]-insulin, the second structurally abnormal mutant insulin, and SerB25]-insulin were semisynthesized and were studied for receptor binding and biological activity. Receptor binding and biological activity determined by its ability to increase 2-deoxy-glucose uptake in rat adipocytes were 0.7-3% of native insulin for SerB24]-insulin and 3-8% for SerB25]-insulin. Negative cooperative effect of these analogues was also markedly decreased. Immunoreactivity of SerB24]-insulin was decreased whereas that of SerB25]-insulin was normal. Markedly decreased receptor binding of SerB24]-insulin appeared to be due to substitution of hydrophobic amino acid, Phe, with a polar amino acid, Ser, at B24.