Sanders N K, Childress J J
Biol Bull. 1990 Jun;178(3):286-294. doi: 10.2307/1541830.
The bathypelagic mysid, Gnathophausia ingens Dohrn, lives aerobically at oxygen partial pressures as low as 6 torr in the oxygen minimum layer off southern California. This study is concerned with the O2 binding properties of this mysid's hemocyanin and the function of the pigment in O2 uptake at low Po2. The effect of temperature on in vivo hemolymph pH (ΔpH/ΔT = -0.018) was measured from 2.5 to 12.5°C. Hemocyanin concentration was estimated to be 24 mg/1, corresponding to an O2 binding capacity of about 0.3 mmol O2/l. Freezing of hemolymph samples significantly decreased the affinity and cooperativity of HcO2 binding, necessitating the use of fresh hemolymph. The HcO2 affinity was high (P50 of 1.4 torr at 5.5°C, pH 7.87), allowing the loading of O2 even at 6 torr. The cooperativity of HcO2 binding was also high (n50 = 3.5 at 5.5°C, pH 7.87); presumably allowing the pigment to function effectively as an O2 transporter within the small Po2 difference between the environment and the tissues. Temperature differences within the environmental range (2-10°C) had no significant effect on the oxygen affinity (ΔH = -6.7 kJ/mol, pH 7.7) or on the cooperativity of O2 binding. A large Bohr shift (Δ log P50/ΔpH = -0.80 to -0.81) was present at all temperatures. L-lactate produced moderate increases in HcO2 affinity (Δ log P50/Δ log [lactate] = -0.13 at pH 7.9) and in cooperativity. Regional and ontogenetic comparisons suggest that regional and ontogenetic differences in HcO2 affinity occur in this species. This mysid has a hemocyanin of unusually high O2 affinity and cooperativity of O2 binding for a crustacean living at low temperatures, and this appears to be an adaptation for oxygen loading and transport at the cold, low oxygen conditions in deep-sea oxygen minimum layers. The reduced temperature sensitivity of HcO2 affinity may also be an adaptation to low oxygen.
深海磷虾Gnathophausia ingens Dohrn在南加利福尼亚州外海的氧含量最小值水层中，能在氧分压低至6托的环境下进行有氧生活。本研究关注这种磷虾血蓝蛋白的氧气结合特性，以及该色素在低氧分压下摄取氧气的功能。在2.5至12.5°C范围内测量了温度对体内血淋巴pH值的影响（ΔpH/ΔT = -0.018）。估计血蓝蛋白浓度为24毫克/升，对应的氧气结合能力约为0.3毫摩尔氧气/升。血淋巴样本冷冻会显著降低血蓝蛋白与氧气结合的亲和力和协同性，因此需要使用新鲜血淋巴。血蓝蛋白与氧气的亲和力较高（在5.5°C、pH 7.87时P50为1.4托），即使在6托的氧分压下也能摄取氧气。血蓝蛋白与氧气结合的协同性也很高（在5.5°C、pH 7.87时n50 = 3.5）；据推测，这使得该色素能够在环境与组织之间较小的氧分压差异范围内有效地作为氧气转运体发挥作用。环境温度范围（2 - 10°C）内的温度差异对氧气亲和力（ΔH = -6.7千焦/摩尔，pH 7.7）或氧气结合的协同性没有显著影响。在所有温度下都存在较大的波尔效应（Δ log P50/ΔpH = -0.80至 -0.81）。L - 乳酸会使血蓝蛋白与氧气的亲和力适度增加（在pH 7.9时，Δ log P50/Δ log [乳酸] = -0.13），并提高协同性。区域和个体发育比较表明，该物种在血蓝蛋白与氧气亲和力方面存在区域和个体发育差异。对于生活在低温环境下的甲壳类动物而言，这种磷虾拥有一种具有异常高的氧气亲和力和氧气结合协同性的血蓝蛋白，这似乎是对深海氧含量最小值水层寒冷、低氧条件下氧气摄取和运输的一种适应。血蓝蛋白与氧气亲和力的温度敏感性降低也可能是对低氧环境的一种适应。
