title: Regulation of crayfish, Orconectes virilis, tail muscle lactate dehydrogenase (LDH) in response to anoxic conditions is associated with alterations in phosphorylation patterns.
abstract: Lactate dehydrogenase (LDH), the terminal enzyme of anaerobic glycolysis, has a crucial role in sustaining ATP production by glycolysis during periods of anoxia via regenerating NAD+through the production of lactate. The present study examined the effects of prolonged (20h) anoxic submergence on LDH from the tail muscle of an anoxia-tolerant crayfish (Orconectes virilis). LDH was purified to homogeneity from tail muscle of both aerobic control and anoxic crayfish in a three step process. Analysis of the kinetic parameters and the stability of LDH showed that the Vmaxin the pyruvate-reducing direction was significantly higher for the enzyme from anoxic crayfish whereas in the lactate-oxidizing direction the Vmaxwas significantly higher for the control enzyme. Differential scanning fluorimetry was used to assess thermal unfolding of crayfish LDH. The results showed that the enzyme from control muscle had a significantly higher melting temperature (greater thermal stability) than the anoxic enzyme form, suggesting that there was a structural difference between the two enzyme forms. Immunoblotting of purified LDH implicated post-translational modification as the reason for this difference; purified LDH from aerobic control crayfish showed significantly higher amounts of serine/threonine phosphorylation than did the anoxic enzyme form. This study provides evidence for anoxia-induced modifications of crayfish muscle LDH that may contribute significantly to modulating enzyme function under anoxic conditions.
authors.affiliation: Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Stuart R
authors.initials: SR
authors.lastname: Green
authors.affiliation: Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada. Electronic address: kenneth_storey@carleton.ca.
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000201:enzymology* / Q000378:metabolism; D004795:Enzyme Stability; D000860:Hypoxia / Q000378:metabolism*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D013623:Tail
chemical_list: D007770:L-Lactate Dehydrogenase
keywords: Anoxia-tolerance; Muscle glycolysis; Orconectes virilis; Posttranslational modification