Unusual variant of lactate dehydrogenase isoenzymes.

Thirteen electrophoretic bands of lactate dehydrogenase isoenzyme activity were detected in the serum of a 69-year-oldNegro 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 lsoenzyme 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 healthydaughters displayeda similar pattern of multiple lsoenzyme 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 pro-S duced, each of which apparently combines with H chains with equal facility, leading to the multiband enzymatic specificity seen.