Department of Physiological Botany, Uppsala University, P.O. Box 540, S-751 21, Uppsala, Sweden.
Planta. 1992 Aug;188(1):1-6. doi: 10.1007/BF00198932.
It has been proposed that many marine macroalgae are able to utilize HCO 3 (-) for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae, Fucus serratus L. and Laminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3',4'-dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO 3 (-) to OH(-) and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.
有人提出，许多海洋大型藻类能够利用 HCO 3 (-) 进行光合作用和生长，并且这个过程涉及能量依赖的离子泵。因此，我们研究了两种海洋大型褐藻——锯齿石莼（Fucus serratus L.）和海带（Laminaria saccharina（L.）Lamour.）在光照下周围介质的碱化作用，目的是研究细胞外碳酸酐酶（EC 4.2.1.1.）在从海水中同化无机碳中的作用。特别是，我们研究了膜不可渗透或缓慢渗透的碳酸酐酶抑制剂对海水碱化速率的影响。在两种物种中，在碱性 pH 值（pH 8.0）下碱化速率受到抑制，但在酸性 pH 值（pH 6.0）下没有观察到抑制。发现碱化作用是光依赖性的，并且被 3-(3',4'-二氯苯基）-1,1-二甲基脲抑制，因此与光合作用相关。先前已经表明，大型藻类的碱化作用与无机碳的吸收成正比。我们认为，在两种被研究的物种中，介质在碱性 pH 值下的碱化主要是细胞外反应的结果。该反应由细胞外碳酸酐酶催化，将 HCO 3 (-) 转化为 OH(-) 和 CO2；然后通过质膜吸收 CO2。然而，我们不排除其他无机碳吸收机制的参与。
