Vol. 37 No. 1, 1998
Structure, Regulation and Evolution of Vertebrate Lactate
of Life Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan 804
Shoei-Lung Li (1998) In vertebrates, L-lactate dehydrogenase
(LDH) isozymes A (muscle) and B (heart) are best suited for pyruvate
reduction and lactate oxidation, respectively. In mammals and columbid
birds, a 3rd LDH-C isozyme is expressed in testis. In advanced teleost
fish a 3rd LDH isozyme is found only in the eye, but in more primitive
teleosts, if it is present, it has a generalized distribution. The
evolutionary relationships among these 3rd forms of LDH isozymes have
not been completely resolved.
We have cloned the cDNAs encoding LDH-A, LDH-B, and/or LDH-C isozymes
from the human, mouse, rat, porcine, pigeon, alligator, lizard, turtle,
Xenopus, and a nematode.
We have determined the exon-intron organization of human LDH-A, LDH-B,
and LDH-C genes, and the complete sequence of 12 851 nucleotides of the
mouse LDH-A gene. The protein-coding sequences of the mammalian LDH-A,
LDH-B, and LDH-C genes, as well as duck LDH-B gene, are interrupted by
6 introns at homologous positions. The expression of vertebrate LDH-A,
LDH-B, and LDH-C genes is tissue specific and developmentally
regulated. Expression of the mammalian LDH-A gene was also shown to be
induced by cAMP and estrogen.
In collaboration with Dr. Wen-Hsiung Li, we analyzed the evolutionary
relationships among vertebrate LDH isoyzmes. Contrary to the common
opinion that the turtle lineage branched off before the divergence
between the lizard/alligator and bird lineages, the turtle lineage was
found clustered with either the alligator lineage or the alligator-bird
clade, while the lizard lineage was found to have branched off before
the divergence between the alligator/turtle and bird lineages. The
pigeon testicular LDH-C gene was evidently duplicated from the LDH-B
(heart) gene, so it is not orthologous to the mammalian testicular
LDH-C genes, which appear to be derived from the LDH-A (muscle) gene.
Key words: Genes,
Isozymes, Protein sequences, Phylogenetic tree.
*Correspondence: Tel: 886-7-5252379. Fax: 886-7-5252360.