Effects of neuraminidase treatment on solubilized insulin receptor

Neuraminidase treatment of triton-solubilized insulin receptors from rat fat cell membranes caused release of sialic acid and changed the isoelectric point (pI) of the insulin receptor from 4.7 to 5.6. Neuraminidase had no effect on the number or affinity of insulin receptors. These results indicate that the insulin receptor contains sialic acid, but that this sialic acid is not involved in the binding reaction.