Palmqvist Kristin, Badger Murray R
Department of Plant Physiology, Umeå University, S-90187 Umeå, Sweden.
Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, P.O. Box 475, Canberra 2601 ACT, Australia.
New Phytol. 1996 Apr;132(4):627-639. doi: 10.1111/j.1469-8137.1996.tb01881.x.
The activity of the enzyme carbonic anhydrase (CA; E.C. 4.2.1.1) was examined in eight species of lichen in vivo by measurements of O exchange from doubly labelled CO ( C O O) to water, with the aim of determining whether this enzyme is present in lichens and if so to what extent it participates in physiological processes. The lichens were chosen to represent different mycobiont (Heterodera, Leptogium, Lobaria, Peltigera, Pseudocyphellaria, Xantoparmelia) and photobiont (Coccomyxa, Dictyochloropsis, Myrmecia, Nostoc, Trebouxia) genera as well as varying morphology. All lichens were found to possess considerable activity of CA, which varied by a factor of about four between the species when compared on a chlorophyl basis, and by u factor of about 10 when related to the weight. Incubation of lichen tholli with ethoxyzolamide (EZA) and acetazolamide (AZA), which inhibit intracellular and extracellular CA respectively, showed that intracellular CA was present in all of the species. Incubation with EZA also resulted in inhibition of photosynthetic CO , uptake in all species suggesting a role of internal CA in the CO , acquisition process in all the investigated photobiont genera. A part of the CA activity was inhibited by AZA in all except two of the four cyanobacterial Nostoc lichens, indicating the possible presence of extracellular forms of CA. This CA also appeared to be involved in the acquisition of CO , as AZA inhibited photosynthetic CO uptake in these lichens. The CA inhibitors also affected CO efflux in the dark, i.e. fungal respiration, which was inhibited by both AZA and EZA in six of the species, suggesting that a proportion of the CA activity might be located in the mycobiont.
通过测量双标记的CO₂（¹⁴C¹⁸O₂）与水之间的氧交换，在体内检测了八种地衣中碳酸酐酶（CA；E.C. 4.2.1.1）的活性，目的是确定这种酶是否存在于地衣中，以及如果存在，它在生理过程中的参与程度如何。选择这些地衣以代表不同的真菌共生体（异层地衣属、薄皮地卷属、肺衣属、皮果衣属、拟杯点衣属、黄髓盘衣属）和光合共生体（绿球藻属、拟绿球藻属、蚁巢藻属、念珠藻属、橘色藻属）属以及不同的形态。所有地衣都被发现具有相当高的CA活性，以叶绿素为基础比较时，物种之间的活性变化约为四倍，而与重量相关时变化约为十倍。用地衣体与分别抑制细胞内和细胞外CA的乙氧唑胺（EZA）和乙酰唑胺（AZA）一起孵育，表明所有物种中都存在细胞内CA。用EZA孵育还导致所有物种的光合CO₂吸收受到抑制，这表明内部CA在所有研究的光合共生体属的CO₂获取过程中发挥作用。除了四种蓝藻念珠藻地衣中的两种之外，所有地衣中AZA都抑制了一部分CA活性，这表明可能存在细胞外形式的CA。这种CA似乎也参与了CO₂的获取，因为AZA抑制了这些地衣中的光合CO₂吸收。CA抑制剂也影响了黑暗中的CO₂外流，即真菌呼吸，六个物种中的AZA和EZA都抑制了真菌呼吸，这表明一部分CA活性可能位于真菌共生体中。
