LDH isoenzymes in muscle diseases.

The LDH isoenzyme pattern was investigated in biopsy material of muscles of children suffering from progressive muscular dystrophy and other neurogenic muscular disorders. An absence or pronounced activity loss of LDH 5 was observable in most of the cases. The proportion of subunits was the same in the diseased and the control muscles. Comparing the measured isoenzyme patterns with those expected from a random coupling of of the subunits, a lower percentage of LDH 5 and a higher one of LDH 4 was detected. The cause of the absence of LDH 5 is not a disturbance of M subunit synthesis but the post-translational inhibition of the tetramer forming process of the synthetised M subunits.