Carbonic anhydrase (CA) is an abundant protein in most photosynthesizing organisms and higher plants. This review paper considers the physiological importance of the more abundant CA isoforms in photosynthesis, through their effects on CO2 diffusion and other processes in photosynthetic organisms. In plants, CA has multiple isoforms in three different families (α, β and γ) and is mainly known to catalyze the CO2 ↔ HCO 3 - equilibrium. This reversible conversion has a clear role in photosynthesis, primarily through sustaining the CO2 concentration at the site of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Despite showing the same major reaction mechanism, the three main CA families are evolutionarily distinct. For different CA isoforms, cellular localization and total gene expression as a function of developmental stage are predicted to determine the role of each family in relation to the net assimilation rate. Reaction-diffusion modeling and observational evidence support a role for CA activity in reducing resistance to CO2 diffusion inside mesophyll cells by facilitating CO2 transfer in both gas and liquid phases. In addition, physical and/or biochemical interactions between CAs and other membrane-bound compartments, for example aquaporins, are suggested to trigger a CO2 -sensing response by stomatal movement. In response to environmental stresses, changes in the expression level of CAs and/or stimulated deactivation of CAs may correspond with lower photosynthetic capacity. We suggest that further studies should focus on the dynamics of the relationship between the activity of CAs (with different subcellular localization, abundance and gene expression) and limitations due to CO2 diffusivity through the mesophyll and supply of CO2 to photosynthetic reactions.

中文翻译：

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碳酸酐酶在叶肉电导和光合作用中的新兴作用。

碳酸酐酶（CA）在大多数光合作用生物和高等植物中是一种丰富的蛋白质。这篇综述文章通过在光合作用中对CO2扩散和其他过程的影响，考虑了更丰富的CA同工型在光合作用中的生理重要性。在植物中，CA在三个不同的家族（α，β和γ）中具有多种同工型，并且主要已知可催化CO2↔HCO 3-平衡。这种可逆转化在光合作用中具有明显的作用，主要是通过维持1，5-双磷酸核糖羧化酶/加氧酶（Rubisco）位点处的CO2浓度。尽管显示出相同的主要反应机制，但三个主要的CA家族在进化上是截然不同的。对于不同的CA同工型，预测细胞的定位和总基因表达与发育阶段的关系，以确定每个家族相对于净同化率的作用。反应扩散模型和观察证据支持CA活性通过促进气相和液相中的CO2转移来降低对叶肉细胞内部CO2扩散的抵抗力。另外，建议CA与其他膜结合的区室例如水通道蛋白之间的物理和/或生化相互作用通过气孔运动触发CO 2感测响应。响应于环境压力，CA表达水平的变化和/或CA的刺激失活可能与较低的光合作用能力相对应。