Thermostability Variations of Enzymes in Sea Algae

Abstract

Intraspecific thermostability variations of enzymes and hemoglobin have been reported inseveral species of insect, marine molluscs, and man. The observations on correlations betweensuch variations in wild populations of the pacific abalone, Haliotis discus hannai, and water temperatures in habitat, and on heart rate responses against thermal stresses strongly suggested a probable association between such variations and temperature tolerance of the animals. No suchwork, however, has been reported on aquatic plants or algae. The present paper describes such variations of enzymes in the two species of sea algae, Porphyra yeroensis and Undaria pinnatifida, and analyses the relationships between water temperature in the habitat and the variations in the former species.
Sampled were a total of 83 specimens of P.yezoensis from waters of Yamada, Iwate and Iwaki, Fukushima and of 22 specimens of U. pinnatifida from Sanriku, Iwate. Thallus of eachspecimen was analysed for thermostability variations in the three enzymes according to the methoddescribed before. Vaziations were observed at the three loci coding phosphoglucomutase, phosphoglucose isomerase, and glutamate dehydrogenase in P. yezoensis and those at phosphoglucose isomerase in U. pinnatifida. Close associaticns between water temperatures in habitat and frequencies of thermostability alleles at the three loci strongly suggested existence of temperature-related differential viabilities among these variations.