A new isoenzyme of lactate dehydrogenase associated with sickle cell hemoglobin.

Electrophoretic fractionation of lactate dehydrogenase in the cytoplasm of red blood cells containing various types of hemoglobin has revealed a sixth isoenzyme occurring regularly in individuals in whom the major part of the hemoglobin is of the sickle cell type. The newly discovered fraction occurs between the normally present third and fourth components. This discovery marks the first time that an additional lactate dehydrogenase isoenzyme has been found in connection with a clinical abnormality. The isoenzyme may serve as a genetic and clinical marker.