A novel in-frame deletion mutation in a case of lactate dehydrogenase (LD) H subunit deficiency showing an atypical LD isoenzyme pattern in serum and erythrocytes.
OBJECTIVE
We report a case showing an atypical lactate dehydrogenase (LD) isoenzyme pattern involving deficiency only of LD-1 and LD-2 in serum and erythrocytes. LD activity in serum from this patient was extremely low, similar to complete LD-H deficiency, and also that in erythrocytes was low.


METHODS
The DNA fragment containing exon 1 through 7 of the LD-H gene were amplified by PCR and directly sequenced. Total RNA was prepared from venous blood and the proportion of LD-H cDNA to total LD cDNA was semiquantified.


RESULTS
Genetic analysis by DNA sequencing detected a three base deletion (AAT) at codon 220 of exon 5, which caused a deletion of one asparagine. The present case did not show reduced LD-H expression at the mRNA level in whole blood. Residue 220 is involved in turning beta-J to alpha1-G and is not buried in the interior of the protein. The novel homozygous in-frame deletion mutation at codon 220 may cause a three-dimensional change of the subunit-binding domain.
Sudo
K
K
Department of Laboratory Medicine, Jikei University, Daisan Hospital, Komae City, Tokyo, Japan. kayosudo@jikei.ac.jp
Maekawa
M
M
Houki
N
N
Okuda
T
T
Akizuki
S
S
Magara
T
T
Kawano
K
K
D000328:Adult; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000172:deficiency / Q000235:genetics; D007770:L-Lactate Dehydrogenase / Q000097:blood / Q000172:deficiency* / Q000235:genetics*; D008297:Male; D017384:Sequence Deletion
D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase