CARBODIIMIDE-INDUCED LABELING OF SEA-URCHIN SURFACES (ECHINOIDEA, ECHINODERMATA)

A method for radiolabelling echinoderm body surfaces, using water-solu ble carbodiimide was developed. The number of carboxyl groups reacting with carbodiimide was estimated as 20 to 30 nmole g(-1) dry weight of sea urchin spines. There were no phosphate groups accessible to carbo diimide on the surface coat. Several enzymes were used to release boun d radiolabel from the spines labelled with carbodiimide and radioactiv e amino acid, Results obtained with proteases and hyaluronidase showed that radiolabel was bound to the glycoprotein and/or protein molecule s on the extracellular surface of the spine epidermis.