β-carbonic anhydrases (βCA) accelerate the equilibrium formation between CO₂ and carbonate. Two plant βCA isoforms are targeted to the chloroplast and represent abundant proteins in the range of > 1% of chloroplast protein. While their function in gas exchange and photosynthesis is well-characterized in carbon concentrating mechanisms of cyanobacteria and plants with C4-photosynthesis, their function in plants with C3-photosynthesis is less clear. The presence of conserved and surface-exposed cysteinyl residues in the βCA-structure urged to the question whether βCA is subject to redox regulation. Activity measurements revealed reductive activation of βCA1, whereas oxidized βCA1 was inactive. Mutation of cysteinyl residues decreased βCA1 activity, in particular C280S, C167S, C230S, and C257S. High concentrations of dithiothreitol or low amounts of reduced thioredoxins (TRXs) activated oxidized βCA1. TRX-y1 and TRX-y2 most efficiently activated βCA1, followed by TRX-f1 and f2 and NADPH-dependent TRX reductase C (NTRC). High light irradiation did not enhance βCA activity in wildtype Arabidopsis, but surprisingly in βca1 knockout plants, indicating light-dependent regulation. The results assign a role of βCA within the thiol redox regulatory network of the chloroplast.

中文翻译：

---

植物β-碳酸酐酶的巯基氧化还原调节。

β-碳酸酐酶（βCA）促进CO ₂之间的平衡形成和碳酸盐。两种植物βCA亚型都靶向叶绿体，代表了叶绿体蛋白含量> 1％的丰富蛋白。尽管它们在气体交换和光合作用中的功能在蓝细菌和具有C4光合作用的植物的碳浓缩机制中具有很好的特征，但它们在具有C3光合作用的植物中的功能尚不清楚。βCA结构中存在保守的和表面暴露的半胱氨酸残基，这促使人们质疑βCA是否受氧化还原调节。活性测量显示βCA1的还原活化，而氧化的βCA1没有活性。半胱氨酸残基的突变降低了βCA1活性，特别是C280S，C167S，C230S和C257S。高浓度的二硫苏糖醇或少量的还原的硫氧还蛋白（TRXs）活化了氧化的βCA1。TRX-y1和TRX-y2最有效地激活βCA1，其次是TRX-f1和f2和NADPH依赖性TRX还原酶C（NTRC）。强光照射不会增强野生型拟南芥中的βCA活性，但令人惊讶的是βca1基因敲除植物，表明其依赖光。结果在叶绿体的硫醇氧化还原调节网络中赋予了βCA作用。