The effect of oxidation of the Met27 residue of [125I]monoiodoglucagon on receptor-binding affinity.
When glucagon is iodinated by the chloramine-T method, the Met27 residue is oxidized. This is not the case when the iodination is performed by the lactoperoxidase method. The two preparations can be purified to the same specific activity using QAE-Sephadex A-25 ion exchange chromatography. Receptor-binding studies in isolated rat adipocytes or hepatocytes revealed that the oxidized from possessed an average-binding affinity which is only about two thirds of that of the non-oxidized form. The reduced affinity of the oxidized tracer cannot be explained by an increased rate of dissociation.
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D002700:Chloramines; D005934:Glucagon / Q000031:analogs & derivatives* / Q000378:metabolism; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes; D007700:Kinetics; D007784:Lactoperoxidase; D008099:Liver / Q000378:metabolism*; D008297:Male; D008715:Methionine; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018027:Receptors, Glucagon; D014105:Tosyl Compounds
D002700:Chloramines; D007202:Indicators and Reagents; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D018027:Receptors, Glucagon; D014105:Tosyl Compounds; C016300:chloramine-T; C029482:iodoglucagon; D005934:Glucagon; D008715:Methionine; D007784:Lactoperoxidase