Castaing M, Bursaux E, Poyart C
Eur J Biochem. 1982 Jan;121(3):573-8. doi: 10.1111/j.1432-1033.1982.tb05825.x.
The effect of CO2 on hemoglobin buffering power was studied in purified human hemoglobin A solutions, native and specifically carbamoylated on N-terminal valines, at 26 degrees C and 42 degrees C, in the oxy and deoxy states. Titrations were performed by varying Pco2 and by strong acid or base in the absence of CO2. The participation of N-terminal valines to the total buffering power was estimated by subtracting the buffering value measured on carbamoylated hemoglobin solutions from that measured on native hemoglobin solutions. In the absence of CO2 the buffering value of native and modified hemoglobin increased slightly (less than 10%) (a) on going from the deoxy to the oxy state, and (b) on raising the temperature from 26 degrees C to 42 degrees C. In the presence of CO2 the buffering value of Hb increased from 9.1 to 16.6 mol mol Hb4-1 pH-1 and that of HbO2 from 10.1 to 19.6 mol mol Hb4-1 pH-1 when the temperature was raised from 26 degrees C to 42 degrees C. These figures correspond to a rise in the fraction of the total buffering value attributable to N-terminal valines from 11% to 25% for Hb and from 3% to 33% for HbO2. The present results point to a non-specific effect of CO2 within the hemoglobin molecule independent of that of N-terminal valines. This effect nearly doubles the buffering value for CO2 when the temperature is raised, and contributes to pH regulation and CO2 removal in tissues with a high metabolic rate.
在26℃和42℃下，研究了二氧化碳对纯化的人血红蛋白A溶液（天然的以及N端缬氨酸经特异性氨甲酰化的）在氧合和脱氧状态下血红蛋白缓冲能力的影响。通过改变二氧化碳分压以及在无二氧化碳时用强酸或强碱进行滴定。通过从天然血红蛋白溶液测得的缓冲值中减去在氨甲酰化血红蛋白溶液上测得的缓冲值，来估算N端缬氨酸对总缓冲能力的贡献。在无二氧化碳时，（a）从脱氧状态转变为氧合状态，以及（b）将温度从26℃升高到42℃时，天然和修饰血红蛋白的缓冲值略有增加（小于10%）。在有二氧化碳存在时，当温度从26℃升高到42℃时，血红蛋白的缓冲值从9.1增加到16.6 mol·mol Hb⁻⁴·pH⁻¹，氧合血红蛋白的缓冲值从10.1增加到19.6 mol·mol Hb⁻⁴·pH⁻¹。这些数据对应于总缓冲值中可归因于N端缬氨酸的部分，血红蛋白从11%增加到25%，氧合血红蛋白从3%增加到33%。目前的结果表明，二氧化碳在血红蛋白分子内存在一种与N端缬氨酸无关的非特异性效应。当温度升高时，这种效应使二氧化碳的缓冲值几乎增加一倍，并有助于高代谢率组织中的pH调节和二氧化碳清除。
