D- and L-lactate dehydrogenases during invertebrate evolution

Area of Science:

• Biochemistry
• Evolutionary Biology
• Genetics

Background:

• L-lactate and D-lactate dehydrogenases (LDH) are evolutionarily distinct enzyme families.
• L-LDH gene evolution, particularly in invertebrates, remains understudied despite its role as a model for gene duplication.
• Previous research suggested L-LDH and D-LDH were mutually exclusive, but recent findings indicate mammals possess both forms.

Purpose of the Study:

• To investigate the phylogenetic relationships of invertebrate L-LDH and D-LDH, with a focus on crustaceans.
• To explore gene duplication events in the evolution of L-Ldh.
• To determine if L-LDH and D-LDH are mutually exclusive across different taxa.

Main Methods:

• Phylogenetic analyses of L-LDH sequences.
• Comparative sequence analysis of D-LDH.
• Identification and characterization of LDH genes in various invertebrate and vertebrate species.

Main Results:

• Phylogenetic analyses of L-LDH in vertebrates align with existing models of gene duplication for LDH-A, LDH-B, and LDH-C.
• Multiple gene duplication events were identified in the crustacean Daphnia pulex and the leech Helobdella robusta.
• Amino acid sequences similar to mammalian D-LDH and yeast DLD1 were found in both vertebrates and invertebrates.

Conclusions:

• The co-occurrence of L-Ldh and D-Ldh genes in chordates and invertebrates indicates they are not mutually exclusive.
• The evolution of L-Ldh in both vertebrates and invertebrates has involved numerous gene duplication events, suggesting a shared evolutionary trajectory.
• High sequence similarity among D-LDH sequences points to a common evolutionary origin.