Premature termination mutations in two patients with deficiency of lactate dehydrogenase H(B) subunit.

Two patients with low lactate dehydrogenase (LD) activity were discovered during healthcare examinations and were found to be homozygous for LD-H (heart) subunit deficiency by electrophoretic isoenzyme analysis of serum and erythrocyte hemolysate. The molecular nature of the genetic mutations was characterized by amplification by the polymerase chain reaction and DNA sequencing. In one case, a single-base substitution (T-->G transversion) at codon 147 of the LD-H(B) gene resulted in a nonsense mutation; in the other case, a deletion of 2 base pairs had occurred at codon 139, resulting in a frameshift translation and premature termination.