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Enzyme Research
Volume 2013, Article ID 784973, 8 pages
http://dx.doi.org/10.1155/2013/784973
Research Article

Purification and Properties of White Muscle Lactate Dehydrogenase from the Anoxia-Tolerant Turtle, the Red-Eared Slider, Trachemys scripta elegans

Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6

Received 24 September 2012; Revised 17 December 2012; Accepted 17 January 2013

Academic Editor: Paul Engel

Copyright © 2013 Neal J. Dawson et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Lactate dehydrogenase (LDH; E.C. 1.1.1.27) is a crucial enzyme involved in energy metabolism in muscle, facilitating the production of ATP via glycolysis during oxygen deprivation by recycling NAD+. The present study investigated purified LDH from the muscle of 20 h anoxic and normoxic T. s. elegans, and LDH from anoxic muscle showed a significantly lower (47%) for L-lactate and a higher value than the normoxic form. Several lines of evidence indicated that LDH was converted to a low phosphate form under anoxia: (a) stimulation of endogenously present protein phosphatases decreased the of L-lactate of control LDH to anoxic levels, whereas (b) stimulation of kinases increased the of L-lactate of anoxic LDH to normoxic levels, and (c) dot blot analysis shows significantly less serine (78%) and threonine (58%) phosphorylation in anoxic muscle LDH as compared to normoxic LDH. The physiological consequence of anoxia-induced LDH dephosphorylation appears to be an increase in LDH activity to promote the reduction of pyruvate in muscle tissue, converting the glycolytic end product to lactate to maintain a prolonged glycolytic flux under energy-stressed anoxic conditions.