ENZYMES IN ANTARCTIC FISH - GLUCOSE-6-PHOSPHATE-DEHYDROGENASE AND GLUTAMATE-DEHYDROGENASE

Glucose-6-phosphate dehydrogenase (G6PD) and L-glutamate dehydrogenase (GDH) from Antarctic fish were isolated and characterized. G6PD was p urified from the erythrocytes of red-blooded Dissostichus mawsoni and from the colorless blood of the icefish Chionodraco hamatus. Structura l and functional characterization showed that the two enzymes do not d iffer significantly from each other. GDH was purified from the liver o f the icefish Chaenocephalus aceratus. As in other fish GDHs, it showe d a marked preference for NAD(+). The amino acid sequence of the activ e-site peptide is virtually identical to that of other fish and verteb rate counterparts. Although the basic structural features of the Antar ctic enzymes are similar to those of mesophilic organisms, some cataly tic and thermodynamic properties make the Antarctic enzymes more suite d to cold-adapted organisms. (C) 1997 Elsevier Science Inc.