Inorganic carbon acquisition by Dunaliella tertiolecta (Chlorophyta) involves external carbonic anhydrase and direct HCO3 − utilization insensitive to the anion exchange inhibitor DIDS
Inorganic carbon acquisition by Dunaliella tertiolecta (Chlorophyta) involves external carbonic anhydrase and direct HCO3 − utilization insensitive to the anion exchange inhibitor DIDS
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DOI：
10.1080/09670260110001735228
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发表时间：
2001-02
影响因子：
2.4
通讯作者：
E. Young;J. Beardall;M. Giordano
中科院分区：
文献类型：
--
作者：
E. Young;J. Beardall;M. Giordano
绿色藻类对阴离子交换抑制剂4，4 ′-二异硫氰基二苯乙烯-2，2 ′-二磺酸（DIDS）的高敏感性是其吸收碳酸氢根的机制。在这项研究中，DIDS抑制杜氏藻的净氧释放高达22%，但内部pH调节，细胞内CO2积累，碳固定和溶解无机碳（DIC）的杜氏藻的亲和力表现出低或不显着的敏感性DIDS。然而，在pH9.5条件下生长和测试的细胞中，用DIDS处理提高了k 0.5（HCO 3 −），这表明DIDS敏感的阴离子交换型HCO 3 −转运蛋白在D.相反，显着的外部碳酸酐酶（CAext）的活性和高达70%的抑制DIC依赖的O2释放乙酰唑胺（AZ）表明，CAext在DIC收购D。此外，在AZ存在的情况下，在高pH值下DIC依赖的光合作用速率比计算的HCO 3 −的CO2供应的未催化速率高12倍。这需要一些系统来直接吸收HCO 3 −。tertiolecta，其可能包括DIDS不敏感机制。DIDS对DIC获得的间接测量的影响应谨慎解释，因为DIDS可能对整个细胞功能产生非特异性影响，并影响与HCO 3 −摄取不直接相关的离子转运过程。
A mechanism of bicarbonate uptake with a high sensitivity to the putative anion-exchange inhibitor 4,4′-diisothiocyanostilbene-2,2′- disulphonic acid (DIDS) has been previously reported in green algae. In this study, DIDS inhibited net oxygen evolution by Dunaliella tertiolecta by up to 22%, but internal pH regulation, intracellular CO2 accumulation, carbon fixation and affinity for dissolved inorganic carbon (DIC) in Dunaliella tertiolecta showed low or insignificant sensitivity to DIDS. However, in cells grown and tested at pH 9·5, treatment with DIDS elevated the k 0.5(HCO3 −), suggesting there may be a minor role for a DIDS-sensitive anion-exchange-type HCO3 − transporter in DIC acquisition by D. tertiolecta at high pH. In contrast, significant external carbonic anhydrase (CAext) activity and up to 70% inhibition of DIC-dependent O2 evolution by acetozolamide (AZ) suggest that CAext has an important role in DIC acquisition in D. tertiolecta, in normal seawater conditions and at elevated pH. Furthermore, the rate of DIC-dependent photosynthesis at high pH, in the presence of AZ, was 12 times higher than the calculated uncatalysed rate of CO2 supply from HCO3 −. This requires some system for direct HCO3 − uptake by D. tertiolecta, which may include a DIDS-insensitive mechanism. The effects of DIDS upon indirect measures of DIC acquisition should be interpreted cautiously as DIDS may have non-specific effects upon whole cell function, and affect ion transport processes not directly related to HCO3 − uptake.