Price G D, Badger M R
Plant Environmental Biology Group, Research School of Biological Sciences, Australian National University, P.O. Box 475, Canberra City, A.C.T. 2601, Australia.
Plant Physiol. 1989 Jan;89(1):37-43. doi: 10.1104/pp.89.1.37.
In high inorganic carbon grown (1% CO(2) [volume/volume]) cells of the cyanobacterium Synechococcus PCC7942, the carbonic anhydrase (CA) inhibitor, ethoxyzolamide (EZ), was found to inhibit the rate of CO(2) uptake and to reduce the final internal inorganic carbon (C(i)) pool size reached. The relationship between CO(2) fixation rate and internal C(i) concentration in high C(i) grown cells was little affected by EZ. This suggests that in intact cells internal CA activity was unaffected by EZ. High C(i) grown cells readily took up CO(2) but had little or no capacity for HCO(3) (-) uptake. These cells appear to possess a CO(2) utilizing C(i) pump that has a CA-like function associated with the transport step such that HCO(3) (-) is the species delivered to the cell interior. This CA-like step may be the site of inhibition by EZ. Low C(i) grown cells possess both CO(2) uptake and HCO(3) (-) uptake activities and EZ inhibited both activities to a similar degree, suggesting that a common step in CO(2) and HCO(3) (-) uptake (such as the C(i) pump) may have been affected. The inhibitor had no apparent effect on internal CO(2)/HCO(3) (-) equilibria (internal CA function) in low C(i) grown cells.
在高无机碳环境（1% CO₂[体积/体积]）中生长的蓝藻聚球藻PCC7942细胞里，发现碳酸酐酶（CA）抑制剂乙氧唑胺（EZ）可抑制CO₂摄取速率，并减小最终达到的内部无机碳（Cᵢ）库大小。EZ对高Cᵢ生长细胞中CO₂固定速率与内部Cᵢ浓度之间的关系影响不大。这表明在完整细胞中，内部CA活性不受EZ影响。高Cᵢ生长细胞容易摄取CO₂，但对HCO₃⁻的摄取能力很小或没有。这些细胞似乎拥有一种利用CO₂的Cᵢ泵，该泵在运输步骤中具有类似CA的功能，使得HCO₃⁻是输送到细胞内部的物质。这个类似CA的步骤可能是EZ的抑制位点。低Cᵢ生长细胞同时具备CO₂摄取和HCO₃⁻摄取活性，且EZ对这两种活性的抑制程度相似，这表明CO₂和HCO₃⁻摄取的一个共同步骤（如Cᵢ泵）可能受到了影响。该抑制剂对低Cᵢ生长细胞中的内部CO₂/HCO₃⁻平衡（内部CA功能）没有明显影响。
