Effects of glycosylation on physiological and biological activities of substances

Hemoglobin A1 (HbA1) increases in old erythrocytes. These erythrocytes with increased HbA1 had decreased oxygen dissociation ability, resulting in decreased function. L-Triiodothyronine (T3) underwent glycosylation to form glycosylated T3. The biological activity of glycosylated T3 was assayed utilizing the metamorphosis of tadpoles. It was found that glycosylated T3 was less than one-tenth as biologically active as T3.