Oxygen binding characteristics of the hemocyanins of two deep-sea hydrothermal vent crustaceans

Effects of pH and temperature on hemocyanin oxygen binding were examined using dialyzed blood from the hydrothermal vent crustaceans Bythograea thermydron (Brachyura) and Alvinocaris lusca (Caridea); blood samples were dialyzed against physiological salines having the same inorganic ion concentration as the blood. Hemocyanin of dialyzed B. thermydron blood demonstrated the highest O2 affinity at 10 degrees C (P50 = 1.8, 3.4 and 4.5 Torr at pH = 8.01, 7.7 and 7.4, respectively), with lower affinities at both higher and lower temperatures for all experimental pH values. A moderate Bohr effect (delta logP50/delta pH = -0.34 to -0.67) was found at all experimental temperatures (2-20 degrees C, pH 7.4-8.01), and a CO2 effect, independent of the pH Bohr effect, was measured at 5 degrees C. Hill coefficients varied widely (n50 = 0.95-3.95) and did not appear to vary with temperature or pH. The hemocyanin oxygen binding properties of B. thermydron blood are not affected by dialysis against salines having the same inorganic ion composition as the blood. Hemocyanin of dialyzed blood from A. lusca demonstrated a reverse temperature effect and a large Bohr effect (delta logP50/delta pH = -0.77 at 5 degrees C, pH 7.4-7.7). Functional aspects of oxygen binding are discussed in relation to the hydrothermal vent environment, and in the context of recent work on crustacean hemocyanins.