[Temperature causes structural and functional changes in lactate dehydrogenase from fish skeletal muscles]

Adaptation of fishes to low and high environmental temperatures gives rise to certain changes in kinetic and structural properties of LDH from skeletal muscles. The KM versus temperature plot for pyruvate of the enzyme isolated from fishes adapted to low temperatures has a minimum at low measurement temperatures, whereas adaptation to high temperatures leads to the enzyme showing a minimum at high temperatures. The LDH isolated from fishes adapted to low environmental temperatures is more stable relative to both thermal and urea-induced inactivation. The differences in the kinetic properties of the enzymes from fishes adapted to low and high temperatures disappear after treatment with urea and subsequent reactivation.