Internal carbonic anhydrase activity in the tissue of scleractinian corals is sufficient to support proposed roles in photosynthesis and calcification
Internal carbonic anhydrase activity in the tissue of scleractinian corals is sufficient to support proposed roles in photosynthesis and calcification
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DOI：
10.1242/jeb.118182
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发表时间：
2015-07-01
影响因子：
2.8
通讯作者：
Fitt, William K.
中科院分区：
文献类型：
--
作者：
Hopkinson, Brian M.;Tansik, Anna L.;Fitt, William K.
造礁珊瑚输入无机碳（Ci）来构建碳酸钙骨架，并支持其组织中共生藻类的光合作用。已知为光合作用和钙化提供Ci的内部途径涉及碳酸酐酶（CA），其使CO2和HCO 3-相互转化。我们已经开发了一种方法用于绝对定量的内部CA（伊卡）的活性在珊瑚组织的基础上的O-18-从标记的CI去除率。该方法应用于三种加勒比海珊瑚（Orbicella faveolata，Porites astreoides和Siderastrea radians），并显示这些物种具有相似的单位表面积伊卡活性，但S。radians的每单位组织体积的伊卡活性高10倍。珊瑚Ci处理的模型表明，测得的伊卡活动是足够的支持拟议的作用，伊卡在Ci运输光合作用和钙化。即使伊卡活性均匀分布在整个珊瑚中，情况也是如此，但该模型表明，将伊卡集中在钙化（钙化液）和光合作用（口腔内胚层）发生的空间中是有利的。我们认为，由于光合作用和钙化率每单位表面积之间的珊瑚研究在这里是相似的，面积伊卡活动用于提供这些反应的CI也应该是相似的。单位体积S.与其他物种相比，弧度可能是由于该物种的有效组织厚度较薄。
Reef-building corals import inorganic carbon (Ci) to build their calcium carbonate skeletons and to support photosynthesis by the symbiotic algae that reside in their tissue. The internal pathways that deliver Ci for both photosynthesis and calcification are known to involve the enzyme carbonic anhydrase (CA), which interconverts CO2 and HCO3-. We have developed a method for absolute quantification of internal CA (iCA) activity in coral tissue based on the rate of O-18-removal from labeled Ci. The method was applied to three Caribbean corals (Orbicella faveolata, Porites astreoides and Siderastrea radians) and showed that these species have similar iCA activities per unit surface area, but that S. radians has similar to 10-fold higher iCA activity per unit tissue volume. A model of coral Ci processing shows that the measured iCA activity is sufficient to support the proposed roles for iCA in Ci transport for photosynthesis and calcification. This is the case even when iCA activity is homogeneously distributed throughout the coral, but the model indicates that it would be advantageous to concentrate iCA in the spaces where calcification (the calcifying fluid) and photosynthesis (the oral endoderm) take place. We argue that because the rates of photosynthesis and calcification per unit surface area are similar among the corals studied here, the areal iCA activity used to deliver Ci for these reactions should also be similar. The elevated iCA activity per unit volume of S. radians compared with that of the other species is probably due to the thinner effective tissue thickness in this species.