Effects of temperature acclimation on lactate dehydrogenase of cod (Gadus morhua): genetic, kinetic and thermodynamic aspects

• Published in: Journal of Experimental Biology
• Main Authors: Zakhartsev, Maxim, Johansen, Torild, Pörtner, Hans O., Blust, Ronny
• Format: Text
• Language: English
• Published: Company of Biologists 2004
• Subjects: Research Article; Gadus morhua
• Online Access: http://jeb.biologists.org/cgi/content/short/207/1/95; https://doi.org/10.1242/jeb.00708

The aim of this study was to determine the effects of seasonal temperature variation on the functional properties of lactate dehydrogenase (LDH) from white muscle and liver of Norwegian coastal cod ( Gadus morhua ) and the possible relevance of LDH allelic variability for thermal acclimation. Two groups of fishes were acclimated to 4°C or 12°C for one year. Polymorphism was observed in only one ( Ldh-B ) of the three Ldh loci expressed in cod liver and/or muscle. Isozyme expression remained unchanged regardless of acclimation temperature ( T A ). The products of locus Ldh-B comprise only 14–19% (depending on the tissue) of total LDH activities and, consequently, differences between phenotypes are negligible in terms of their effect on LDH total performance. No kinetic (<f>K <rm>m</rm> <rm>PYR</rm></f>, <f>K <rm>si</rm> <rm>PYR</rm></f>, V max ) or thermodynamic ( E a , Δ G ) differences were found among Ldh-B phenotypes. Clear kinetic differences were observed between LDH isoforms in the two tissues. However, the Arrhenius activation energy ( E a ) for pyruvate reduction was the same for both tissues ( E a =47 kJ mol–1) at T A =12°C. Factors T A , tissue and phenotype did not reveal a significant effect on the Gibbs free energy change (Δ G ) of the reaction (55.5 kJ mol–1). However, at T A =4°C, the E a was increased ( E a =53–56 kJ mol–1) and the temperature dependence of the constant of substrate inhibition for pyruvate (<f>K <rm>si</rm> <rm>PYR</rm></f>) decreased in both muscle and liver. In conclusion, the strategies of LDH adjustment to seasonal temperature variations in cod involve changes in LDH concentration (quantitative), adjustment of thermodynamic ( E a ) and kinetic (<f>K <rm>si</rm> <rm>PYR</rm></f>) properties of the LDH (modulative) but not the expression of alternative isoforms (qualitative). We assume that the observed increase in E a and the decrease ...