Evolutionary relations among vertebrate muscle-type lactate dehydrogenases

Area of Science:

• Evolutionary biology
• Biochemistry
• Genomics

Background:

• Gene duplication created lactate dehydrogenase A (LDH-A) and LDH-B isozymes in vertebrates.
• Biochemical properties suggested LDH-A and LDH-B loci are orthologous across vertebrates.
• Previous phylogenetic studies questioned a common evolutionary history for LDH-A, especially in lower vertebrates.

Purpose of the Study:

• To investigate the evolutionary history of LDH-A isozymes.
• To determine if teleost fish LDH-A is orthologous to tetrapod LDH-A.
• To clarify the phylogenetic relationships of lactate dehydrogenase isozymes.

Main Methods:

• Sequencing of muscle-type lactate dehydrogenase (LDH) from Fundulus heteroclitus (a teleost fish).
• Phylogenetic analysis of LDH sequences.
• Comparison of teleost muscle LDH sequence with tetrapod LDH-A sequences.

Main Results:

• The sequenced teleost muscle LDH is phylogenetically unrelated to tetrapod LDH-A isozymes.
• While sharing some features with tetrapod LDH-A, phylogenetic analyses do not support orthology between teleost and tetrapod LDH-A isozymes.
• The LDH-B sequence from Fundulus heteroclitus was also found to be unrelated to tetrapod LDH-A.

Conclusions:

• Phylogenetic analyses do not support an orthologous relationship among LDH-A isozymes of teleost fish and tetrapod vertebrates.
• The evolutionary history of LDH-A is more complex than previously assumed based on biochemical properties.
• Gene duplication and subsequent evolution of LDH isozymes vary significantly across vertebrate lineages.