title: Pressure-adaptive differences in lactate dehydrogenases of three hagfishes: Eptatretus burgeri, Paramyxine atami and Eptatretus okinoseanus.
abstract: The tolerance of abyssal pressures likely depends on adaptive modifications of fish proteins. However, structural modifications of proteins which allow functioning at high pressure remain unclear. We compared the activities of lactate dehydrogenase (LDH), an important enzyme in glycolytic reaction, in three hagfishes inhabiting different depths under increased pressure. LDH in Eptatretus okinoseanus, found at a depth of 1,000 m, was highly active at high pressure of 100 MPa maintaining the activity at 70% of that at 0.1 MPa. In contrast, LDH activity in Paramyxine atami, found at 250-400 m, decreased to 55% at 15 MPa, and that in Eptatretus burgeri, found at 45-60 m, was completely absent at 5 MPa. The result suggests that subunit interaction of the LDH-tetramer is more stable in E. okinoseanus than that in P. atami and E. burgeri under high-pressure conditions. We found six amino acid substitutions between the three LDH primary structures. Accordingly, these amino acid residues are likely to contribute to the stability of the E. okinoseanus LDH under high-pressure conditions.
authors.affiliation: Faculty of Pharmaceutical Science, Toho University, Toho, Japan. guchi@phar.toho-u.ac.jp
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nishiguchi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Miwa
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Abe
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D004795:Enzyme Stability; D029941:Fish Proteins / Q000378:metabolism*; D006196:Hagfishes / Q000378:metabolism*; D006874:Hydrostatic Pressure; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D020539:Sequence Analysis, Protein
chemical_list: D029941:Fish Proteins; D021122:Protein Subunits; D007770:L-Lactate Dehydrogenase