A novel missense mutation in human lactate dehydrogenase B-subunit gene

Reduced activity of serum lactate dehydrogenase (LDH; EC 1.1.1.27) was foun d in a male medical student during practical examinations of his own blood. Serum LDH isoenzyme pattern showed reductions in activities of the isoenzy mes with lower subunit A/B ratios such as LDH1 and LDH2. These findings wer e indicative of a partial LDH-B subunit deficiency, which was confirmed in erythrocyte hemolysates by Western blotting. Polymerase chain reaction (PCR )-based DNA sequence analysis of the LDH-B subunit gene revealed a heterozy gous nucleotide change: a guanine to adenine substitution in codon 69 (GGG --> GAG) at the third exon of the LDH-B subunit gene that resulted in a gly cine to glutamic acid substitution (G69E). The mutation was confirmed by PC R-restriction fragment length polymorphism (RFLP) analysis using a mismatch ed primer to introduce a new NcoI restriction site. The same heterozygous m utation was found in his mother but not in other family members. This mutat ion involves a residue belonging to alphaC helix in LDH-B subunit protein m olecule that functions as an interface for other subunits. (C) 2001 Academi c Press.