Hemocyanin is a large, multi-subunit respiratory protein present in arthropods and mollucs. They circulate extracellularly in hemolymph. Hemocyanins do not contain iron but bind oxygen at an active site containing copper atoms ligated by protein side chains.
Keyhole limpet hemocyanin has been used traditionally as a protein carrier for hapten-carrier conjugates in immunochemistry. Keyhole limpet hemocyanin (KLH) has been regarded as a superior carrier. Affinity isolated antibody to hemocyanin may be used as a control reagent for the preparation and immunization of hapten-carrier conjugates.
