Periplasmic or external carbonic anhydrases (CAs) have been well accepted as playing a crucial role in the acquisition of dissolved inorganic carbon; however, no cytological evidence or molecular information on these enzymes has been reported in seaweeds to date. In this study, the full‐length cDNA sequence coding for a putative periplasmic Sjα‐CA2 was cloned from the gametophytes of Saccharina japonica, an industrial brown seaweed. It was 1,728 bp in length and included a 263‐bp 5′‐untranslated region (UTR), a 577‐bp 3′‐UTR, and an 888‐bp open reading frame encoding a protein precursor consisting of 295 amino acids. The mature protein, after removal of a predicted 28‐residue signal peptide, was composed of 267 amino acids with a relative molecular weight of 29.27 kDa. Multisequence alignment and phylogenetic analysis indicated that it was a member of the α‐CA family. Enzyme activity assays showed that the recombinant Sjα‐CA2 in Escherichia coli possessed CO₂ hydration and esterase activities, thus identifying this gene Sjα‐CA2 in function. Immunogold electron microscopic observations with the prepared anti‐Sjα‐CA2 polyclonal antibody illustrated that Sjα‐CA2 was located in periplasmic space of the kelp gametophyte cells. Quantitative real‐time PCR results revealed that the transcription of Sjα‐CA2 was induced by elevated levels, but it was little changed while the kelp gametophytes were subjected to elevated CO₂ concentrations. This study suggests that the periplasmic Sjα‐CA2 might play a role in adapting to elevated environmental levels of by dehydration of to generate CO₂, which could be readily taken up by S. japonica gametophytes.

中文翻译：

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鉴定和鉴定日本糖藻配子体中的周质α碳酸酐酶（CA）

周质或外部碳酸酐酶（CA）已被广泛接受，因为它在获取溶解的无机碳中起着至关重要的作用。然而，迄今为止，尚未在海藻中报告有关这些酶的细胞学证据或分子信息。在这项研究中，编码的假定周质Sjα-CA2的全长cDNA序列是从日本糖藻的配子体中克隆的。，一种工业棕色海藻。它的长度为1,728 bp，包括一个263bp的5'-非翻译区（UTR），577-bp的3'-UTR和一个888bp的开放阅读框，其编码由295个氨基酸组成的蛋白质前体。去除预测的28个残基的信号肽后，成熟蛋白由267个氨基酸组成，相对分子量为29.27 kDa。多序列比对和系统发育分析表明它是α-CA家族的成员。酶活性分析表明，大肠杆菌中的重组Sjα-CA2具有CO ₂水合和酯酶活性，因此鉴定出该基因Sjα - CA2在功能上。用制备的抗Sjα-CA2多克隆抗体进行的免疫金电子显微镜观察表明，Sjα-CA2位于海藻配子体细胞的周质空间中。实时定量PCR结果表明，Sjα-CA2的转录受水平升高的诱导，但当海带配子体受到较高的CO ₂浓度时，其变化不大。这项研究表明，周质的Sjα-CA2可能通过脱水产生CO ₂来适应高水平的环境，这很容易被S吸收。粳米配子体。