Plant Carbonic Anhydrases

Atkins, Craig A.; Patterson, Brian D.; Graham, D.

doi:10.1104/pp.50.2.214

Cited by 68 publications

(25 citation statements)

References 20 publications

(10 reference statements)

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“…For the purpose of this model, we assumed a C 3 leaf with chloroplasts containing 1.25 mM Rubisco sites, an electron transport capacity of 90 mmol m 22 s 21 , a chloroplast CO 2 compensation point of 4.1 Pa, and a dark respiration rate of 0.8 mmol m 22 s 21 (Table I). The concentration of CA was based on in vitro and in vivo activity measurements (Atkins et al, 1972a(Atkins et al, , 1972bPrice et al, 1994;Peltier et al, 1995;Gillon and Yakir, 2000). Atkins et al (1972a) determined the total CA activity in extracts from a range of species.…”

Section: Parameterization Of the Modelmentioning

confidence: 99%

“…Traditionally, the r i has been divided into two major components : the intercellular air space resistance (from substomatal cavities to the cell surface) and the liquid-phase resistance (from the cell walls to the site of carboxylation). Theoretical and Atkins et al (1972aAtkins et al ( , 1972b; Price et al (1994); Peltier et al (1995); Gillon and Yakir (2000) experimental results suggested that the resistance of the intercellular air spaces is negligible in many cases (Genty et al, 1998;Aalto and Juurola, 2002;Piel et al, 2002), although it accounts for a significant portion of r i in thick, hypostomatous leaves (Parkhurst and Mott, 1990;Parkhurst, 1994). The resistances of the cell wall (25%-50%) and chloroplast envelopes (24%-76%) are considered to make major contributions to the total r i Gillon and Yakir, 2000).…”

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confidence: 99%

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The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion

2011

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Photosynthesis is limited by the conductance of carbon dioxide (CO 2 ) from intercellular spaces to the sites of carboxylation. Although the concept of internal conductance (g i ) has been known for over 50 years, shortcomings in the theoretical description of this process may have resulted in a limited understanding of the underlying mechanisms. To tackle this issue, we developed a three-dimensional reaction-diffusion model of photosynthesis in a typical C 3 mesophyll cell that includes all major components of the CO 2 diffusion pathway and associated reactions. Using this novel systems model, we systematically and quantitatively examined the mechanisms underlying g i . Our results identify the resistances of the cell wall and chloroplast envelope as the most significant limitations to photosynthesis. In addition, the concentration of carbonic anhydrase in the stroma may also be limiting for the photosynthetic rate. Our analysis demonstrated that higher levels of photorespiration increase the apparent resistance to CO 2 diffusion, an effect that has thus far been ignored when determining g i . Finally, we show that outward bicarbonate leakage through the chloroplast envelope could contribute to the observed decrease in g i under elevated CO 2 . Our analysis suggests that physiological and anatomical features associated with g i have been evolutionarily fine-tuned to benefit CO 2 diffusion and photosynthesis. The model presented here provides a novel theoretical framework to further analyze the mechanisms underlying diffusion processes in the mesophyll.

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Section: Parameterization Of the Modelmentioning

confidence: 99%

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confidence: 99%

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion

2011

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“…The presence of two distinct (electrophoretically resolved) enzymes in purified preparations, together with the fact that they appear not to be freely interconvertible lends at least some support to the idea of carbonic anhydrase isoenzymes in the leaves of higher plants (2). While for the Pisumn enzyme preparation the maximum protein and maximum activity were coincident (Fig.…”

Section: Discussionmentioning

confidence: 93%

“…In an electrophoretic study of leaf extracts from many plant species, we have shown (2) that while the carbonic anhydrases from dicotyledons are similar in size to the isolated parsley (16) and spinach (12) enzymes, those from monocotyledons are closer in size to the mammalian carbonic anhydrases.…”

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confidence: 99%

Plant Carbonic Anhydrases

Atkins¹,

Patterson

Graham

1972

Plant Physiol.

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Carbonic anhydrase (EC.4.2.1.1) was purified from leaves of the dicotyledon Pisum sativumrl L. (56-fold) and from leaves of the monocotyledon Tradescantia albiflora . The molecular weight of the Pisumn enzyme was estimated to be 188,000 + 8,000 with subunit sizes of 28,000 ± 3,000 and 56,600 + 3,500. It contained 1 mole zinc per 32,500 + 2,000 g protein. MATERIALS AND METHODSPlant Material. Leaves were taken from Tradescantia albiflora Kunth. which was growing in the field during the southern hemisphere summer. The leaves and stem were taken from 2-to 3-week-old plants of Pisumn sativumi L. cv. Greenfeast (Yates Seeds, Sydney, N.S.W.) which were grown in vermicuLlite in a glasshouse.Buffer Solutions. Unless stated otherwise, the pH value of all buffers was determined at 5 C and all contained 1 mM Na,-EDTA and 0.1 M 2-mercaptoethanol. For enzyme isolation, two buffers at pH 8.3 were used; Buffer A contained 0.3 M tris-SO and buffer B contained 10 mm tris-SO.Isolation of Carbonic Anhydrase from Tradescantia. All operations were carried out at 1 C. Nine kg of leaves were chilled and thoroughly homogenized in a Waring Blendor with 9 liters of buffer A. The homogenate was filtered through two layers of nylon mesh (60 tim hole size; Nycloth Co., Harris Park, N.S.W.) and centrifuged at 35,000g for 40 min. The pellet was discarded, and finely powdered ammonium sulfate was added to the supernatant (0.28 g to each ml) with continuous stirring. After centrifugation (35,000g for 30 min) the pellet was discarded. More ammonium sulfate was added to the supernatant (0.16 g to each ml) and the precipitated enzyme recovered by centrifugation (35,000g for 30 min). The pellet was dissolved in the minimum volume of buffer B and dialyzed against three changes (each 4 liters) of 5 mm tris-SO, buffer, pH 8.3, containing 20 mm ME.4 The ME concentration of the dialysate was adjusted to about 0.1 M, and insoluble material was removed by centrifugation (20,000g for 15 min). The supernatant (245 ml) was mixed with A-50 DEAE-Sephadex (20 g dry weight equilibrated with buffer B) in a Buchner funnel and eluted with 1.2 liters buffer B containing 10 mm Na,SO,. This effluent was discarded, and the enzyme was eluted with 1.2 liters buffer B containing 100 mm Na.,SO,. Following ammonium sulfate precipitation (0.44 g added to each ml) the preparation was dissolved and dialyzed as above. The dialysate was placed on a 2-X 30-cm column of DEAEcellulose (Whatman DE-32) equilibrated with buffer B containing 10 mm Na,SO,, and the enzyme was eluted (see Fig. IA) at 25 ml per hr with a linear Na,SO, gradient (250 ml buffer B with 10 mm Na,SO, in the mixing chamber and 250 ml buffer B with 200 mm Na,SO, in the reservoir). The "active' fractions (within the arrows shown in Fig. 1 A) were pooled, concentrated by ammonium sulfate precipitation (0.44 g added to each ml) to 20 ml, and placed on a 36-x 2.5-cm 'Abbreviations: DEAE: diethylaminoethyl; ME: 2-mercaptoethanol; SDS: sodium dodecylsulfate.

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“…These forms are called isoenzymes; they play a major role in the adaptation of organisms and are used as biochemical co-dominant markers to identify genotypes and establish phylogenetic relationships among different groups of taxa. Carbonic anhydrase isoenzymes have been determined in the 24 monocot and dicot plant species (Atkins et al, 1972).…”

Section: Isoenzymesmentioning

confidence: 99%

Carbonic Anhydrase and Zinc in Plant Physiology

Escudero-Almanza

Barrios

Hernández-Rodríguez

et al. 2012

Chilean J. Agric. Res.

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Carbonic anhydrase (CA) (EC: 2.4.1.1) catalyzes the rapid conversion of carbon dioxide plus water into a proton and the bicarbonate ion (HCO3 -) that can be found in prokaryotes and higher organisms; it is represented by four different families. Carbonic anhydrase is a metalloenzyme that requires Zn as a cofactor and is involved in diverse biological processes including pH regulation, CO2 transfer, ionic exchange, respiration, CO2 photosynthetic fixation, and stomatal closure. Therefore, the review includes relevant aspects about CA morphology, oligomerization, and structural differences in the active site. On the other hand, we consider the general characteristics of Zn, its geometry, reactions, and physiology. We then consider the CA catalysis mechanism that is carried out by the metal ion and where Zn acts as a cofactor. Zinc deficiency can inhibit growth and protein synthesis, and there is evidence that it reduces the CA content in some plants, which is a relationship addressed in this review. In leaves, CA represents 20.1% of total soluble protein, while it is the second most abundant in the chloroplast after ribulose 1,5-disphosphate carboxylase/oxygenase (RuBisCO). This facilitates the supply of CO2 to the phosphoenolpyruvate carboxylase in C4 and CAM plants and RuBisCO in C3 plants.

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Plant Carbonic Anhydrases

Abstract: On the basis of polyacrylamide gradient gel electrophoresis of leaf extracts from 24 species of higher plants, two

Cited by 68 publications

References 20 publications

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion

Plant Carbonic Anhydrases

Carbonic Anhydrase and Zinc in Plant Physiology

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Plant Carbonic Anhydrases

Abstract: On the basis of polyacrylamide gradient gel electrophoresis of leaf extracts from 24 species of higher plants, two

Cited by 68 publications

References 20 publications

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO2 Diffusion

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO2 Diffusion

Plant Carbonic Anhydrases

Carbonic Anhydrase and Zinc in Plant Physiology

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The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO₂ Diffusion