Widdas W F, Baker G F
Department of Biological Sciences, Royal Holloway College, University of London, Egham, Surrey, Great Britain.
Cytobios. 2000;103(402):39-60.
The pH changes due to bubbling CO2 through water produced anomalies which were more readily explained by an hypothesis based on electrostatic attractions between the molecules. The present studies have suggested that an hexagonal array of six carbon dioxide molecules could bind and sequester a hydroxyl anion. The binding energy of the complex is estimated to be comparable with that of a covalent compound and its dissociation may only occur at the water interface with air or at the water/hydrophobic protein interface in a protein cleft. The physiological importance lies in the consequential release of an equal number of free hydrogen ions (H3O+) and the disruption of the normal action of buffer systems in regulating the cytoplasmic pH. The counteraction of this sequestration reaction and the acid-base disturbances which result, form the second important function of carbonic anhydrase isoforms, the mechanisms of which are briefly discussed.
通过向水中通入二氧化碳而导致的pH变化产生了一些异常现象，基于分子间静电吸引的假说能更轻易地解释这些现象。目前的研究表明，由六个二氧化碳分子组成的六边形阵列可以结合并隔离一个羟基阴离子。该复合物的结合能估计与共价化合物的结合能相当，并且其解离可能仅发生在水与空气的界面处，或者发生在蛋白质裂隙中的水/疏水蛋白界面处。其生理重要性在于等量游离氢离子（H3O+）的相应释放以及缓冲系统在调节细胞质pH时正常作用的破坏。这种隔离反应的抵消作用以及由此产生的酸碱紊乱，构成了碳酸酐酶同工型的第二个重要功能，本文将简要讨论其机制。
