High resolution of human lactate dehydrogenase: new multiple forms and potential tumor markers.

Human lactate dehydrogenase (LDH) was investigated by ultrathin-layer polyacrylamide gel isoelectric focusing (IEF). In serum, approximately 15 bands and in lyzates of erythrocytes approximately 20 bands were detected. Known LDH isoenzymes (identified by markers) appeared in the zymograms as follows: LDH-1 as a single or double band, LDH-2 as a single band in serum and in the marker, and as a double band in hemolyzate, LDH-3 as a double band, and LDH-4 and LDH-5 each as a single band. LDH-1 was partly inactivated, probably due to deamidation in the acidic range of the pH gradient. Potential LDH tumor markers were detected in different tumor cytosols.