Purification and characterization of a urea sensitive lactate dehydrogenase from the liver of the African clawed frog, Xenopus laevis

Katzenback, B. A., Dawson, N. J. and Storey, K. B. (2014) Purification and characterization of a urea sensitive lactate dehydrogenase from the liver of the African clawed frog, Xenopus laevis. Journal of Comparative Physiology B: Biochemical, Systems, and Environmental Physiology, 184(5), pp. 601-611. (doi: 10.1007/s00360-014-0824-1) (PMID:24651940)

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Abstract

The African clawed frog, Xenopus laevis, is able to withstand extremely arid conditions by estivating, in conjunction with dehydration tolerance and urea accumulation. Estivating X. laevis reduce their metabolic rate and recruit anaerobic glycolysis, driven by lactate dehydrogenase (LDH; E.C. 1.1.1.27) enzymes that reversibly convert pyruvate and NADH to lactate and NAD+, to meet newly established ATP demands. The present study investigated purified LDH from the liver of dehydrated and control X. laevis. LDH from dehydrated liver showed a significantly higher K m for L-lactate (1.74 fold), NAD+ (2.41 fold), and pyruvate (1.78 fold) in comparison to LDH from the liver of control frogs. In the presence of physiological levels of urea found in dehydrated animals, the K m values obtained for dehydrated LDH all returned to control LDH K m values. Dot blot analysis showed post-translational modifications may be responsible for the kinetic modification as the dehydrated form of LDH showed more phosphorylated serine residues (1.54 fold), less methylated lysine residues (0.43 fold), and a higher level of ubiquitination (1.90 fold) in comparison to control LDH. The physiological consequence of dehydration-induced LDH modification appears to adjust LDH function in conjunction with urea levels in dehydrated frogs. When urea levels are high during dehydration, LDH retains its normal function. Yet, as urea levels drop during rehydration, LDH function is reduced, possibly shunting pyruvate to the TCA cycle.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Dawson, Dr Neal
Authors: Katzenback, B. A., Dawson, N. J., and Storey, K. B.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Journal of Comparative Physiology B: Biochemical, Systems, and Environmental Physiology
Publisher:Springer
ISSN:0174-1578
ISSN (Online):1432-136X
Published Online:21 March 2014

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