Pressure adaptation of Na+/K+-ATPase in gills of marine teleosts.
The effects of pressure and temperature on an integral membrane protein, Na+/K+-adenosine triphosphatase (Na+/K+-ATPase), were studied in fish gill membrane preparations from shallow- and deep-living marine teleosts. The inhibition by pressure of maximal velocity of the enzyme is nonlinear, increasing at higher pressures. Na+/K+-ATPases from deep-sea fish were less inhibited by pressure than those of shallow-living species. Habitat temperature also affected the pressure response of the enzyme. As a function of physiological pressure and temperature, the order of increasing pressure-sensitivity was cold, deep-sea less than warm, deep-sea (hydrothermal vents) less than polar = shallow and mid-depth, cold less than shallow, warm. Activation volumes in all species were conserved at 30-60 ml mol-1 at physiological pressures, which may reflect a similar membrane physical state at the actual pressure the animal experiences. Arrhenius plots [In(Na+/K+-ATPase activity) vs 1/T] were steeper for warm-water and shallow-living species than for deep-sea species. The depth at which adaptation was first observed was about 2000 m (approximately equal to 200 atm: 1 atm = 101.3 kPa). The data are consistent with a model of increased membrane fluidity resulting in reduced pressure-sensitivity of Na+/K+-ATPase from deep-sea species.
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Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093.
Somero
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D000064:Acclimatization; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D005399:Fishes / Q000502:physiology*; D005880:Gills / Q000201:enzymology / Q000502:physiology*; D011312:Pressure; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity
D000254:Sodium-Potassium-Exchanging ATPase