Lactate dehydrogenase isoenzymes: Irregularities in electrophoretic mobility

In the sera of five patients out of a group of several thousand the LDH-isoenzymes showed abnormal mobilities upon electrophoresis in agar gel. In all five sera LDH₄ was retarded and LDH₅ accelerated. LDH_1–3 were either normal or retarded and in one case LDH₁ and-₂ were entirely absent. Since the zymograms of the erythrocytes and leukocytes of all patients showed normal mobilities, genetic differences in the structure of the LDH molecules could be excluded. Preliminary experiments show that the abnormal mobilities may be caused by a relatively thermostable factor in the serum.NAd added to the patients' sera partly restored the mobilities of their isoenzymes to normal. It is suggested that the serum factor is active by removing or blocking NAD attached to the LDH-molecule, or other moieties of the latter, influencing the electrophoretic mobility. A correlation with liver disease seems very probable. The four-polypeptide chain hypothesis for the LDH-isoenzymes in its present form does not offer sufficient scope to fit in these and other abnormal phenomena hitherto registered in this field.