Clinical Chemistry, Vol 21, 162-164, Copyright © 1975 by the American Association for Clinical Chemistry

Unusual Variant of Lactate Dehydrogenase Isoenzymes

¹ Department of Laboratory Medicine, Yale University School of Medicine, 333 Cedar St., New Haven, Conn. 06510.

Thirteen electrophoretic bands of lactate dehydrogenase isoenzyme activity were detected in the serum of a 69-year-old Negro woman who died of pseudomonas pneumonia. No evidence of tumor was found at necropsy, and additional studies of the enzymatic activity of crude extracts of liver, lung, spleen, kidney, brain, skeletal muscle, lymph node, and heart revealed 1, 2, 3, 4, and 5 separate isoenzyme bands for lactate dehydrogenase isoenzymes 1, 2, 3, 4, and 5, respectively (a total of 15 isoenzyme bands). Serum and erythrocyte hemolysate from one of two healthy daughters displayed a similar pattern of multiple isoenzyme bands in isoenzymes 2 and 3. The observed pattern is consistent with the heterozygous form of a mutation of the genetic locus controlling synthesis of the M monomer such that two differently charged monomeric proteins are produced, each of which apparently combines with H chains with equal facility, leading to the multiband enzymatic specificity seen.