A possible role for carbonic anhydrase in the lumen of chloroplast thylakoids in green algae

2002 ◽  
Vol 29 (3) ◽  
pp. 243 ◽  
Author(s):  
Eddy van Hunnik ◽  
Dieter Sültemeyer
Keyword(s):  
Cell Wall ◽  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Green Algae ◽  
Inorganic Carbon ◽  
Electron Flow ◽  
Photosynthetic Apparatus ◽  
Thylakoid Membranes ◽  
Atp Production ◽  
Atp Formation

In order to understand the function of the lumen carbonic anhydrase (CA) which is bound to PSII at the lumenal side of the thylakoids in chloroplasts of eukaryotic algae, thylakoids were isolated from chloroplasts of Tetraedron minimum, Chlamydomonas noctigama, the cell wall-less mutant Chlamydomonas reinhardtii CW15, and a C. reinhardtii CW15/CIA3 mutant which lacks the lumen CA. The isolated thylakoids produced O2 on illumination and exhibited electron flow between PSII and PSI, indicating that the thylakoids were intact and the photosynthetic apparatus were functional. We could not detect any uptake of HCO3–,nor efflux of CO2, from the thylakoids upon illumination, making it improbable that the CA present in the lumen of the thylakoids would play a role in furnishing CO2 for Rubisco. We were able to determine ATP production upon illumination in isolated thylakoids. Under high inorganic carbon (Ci; 5 mM), all species showed significant amounts of ATP being produced. Under low Ci (200 M), we could not detect ATP formation from C. reinhardtii CW15/CIA3 upon illumination. This mutant was not able to survive more then 4 h of low Ci in culture. We therefore suggest that the lumen CA is not involved in the CO2 concentrating mechanism, but might play a role in the formation of a proton gradient across the thylakoid membranes.

scholarly journals Identification and functional role of the carbonic anhydrase Cah3 in thylakoid membranes of pyrenoid of Chlamydomonas reinhardtii

2012 ◽  
Vol 1817 (8) ◽  
pp. 1248-1255 ◽  
Author(s):  
Maria A. Sinetova ◽  
Elena V. Kupriyanova ◽  
Alexandra G. Markelova ◽  
Suleyman I. Allakhverdiev ◽  
Natalia A. Pronina
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Functional Role ◽  
Thylakoid Membranes

Extracellular carbonic anhydrase of Chlamydomonas reinhardtii: localization, structural properties, and catalytic properties

1991 ◽  
Vol 69 (5) ◽  
pp. 1079-1087 ◽  
Author(s):  
H. David Husic
Keyword(s):  
Plasma Membrane ◽  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Catalytic Properties ◽  
Physiological Role ◽  
Carbon Utilization ◽  
Unicellular Green Alga ◽  
Inorganic Carbon Utilization ◽  
Inorganic Carbon Acquisition

In the unicellular green alga Chlamydomonas reinhardtii, a form of the enzyme carbonic anhydrase that is localized outside of the plasma membrane is an inducible component of a system that is involved in inorganic carbon acquisition and concentration from the growth medium. This article contains a review and analysis of the current literature regarding the extracellular carbonic anhydrase from Chlamydomonas reinhardtii and presents some new studies on its extracellular localization, physiological role in inorganic carbon acquisition, and some of the structural and catalytic properties of the enzyme. Key words: carbonic anhydrase, Chlamydomonas reinhardtii, inorganic carbon utilization.

Adaptation of a Chlamydomonas mutant with reduced rate of photorespiration to different concentrations of CO2

2005 ◽  
Vol 83 (7) ◽  
pp. 834-841 ◽  
Author(s):  
Kensaku Suzuki ◽  
Hidenori Onodera
Keyword(s):  
Chlorophyll Fluorescence ◽  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Electron Flow ◽  
Effective Quantum Yield ◽  
Wild Type ◽  
Chlorophyll Fluorescence Parameters ◽  
Phosphoglycolate Phosphatase ◽  
Concentrating Mechanism ◽  
Type Strains

It has been widely accepted that Chlamydomonas reinhardtii cells utilize inorganic carbon very efficiently for photosynthesis by operating a CO2-concentrating mechanism (CCM) under conditions of limited CO2. To help define the mechanism, 7FR2N, one of the suppressor double mutants of phosphoglycolate phosphatase-deficient (pgp1) mutants that have a reduced photorespiration rate (RPR) was crossed with wild-type strains to generate the strain N21 as a single RPR mutant. The comparison of photosynthetic characteristics with wild-type strains after the cells adapted to different concentrations of CO2 revealed that photosynthetic affinity for inorganic carbon was higher than that in wild-type strains after adaptation to concentrations between 50 µL·L–1 CO2 and 5% CO2. Chlorophyll fluorescence parameters were also compared, and the biggest difference between N21 and the wild-type strains was observed in the photochemical quenching and effective quantum yield of photosystem II (ΔF/Fm′) at the CO2 compensation point. These values in N21 increased in a similar manner to the photosynthetic affinity for CO2, and increased significantly when the cells adapted to low-CO2 levels, whereas the values in the wild-type strains were apparently lower without any significant changes, regardless of the CO2 concentrations to which they were adapted. Although it was not clear if a nonphotochemical quenching parameter (NPQ) in N21 was higher than that in wild-type strains, NPQ increased coincidentally with the increase in photosynthetic affinity for inorganic carbon when the CO2 concentrations to which the strains were adapted decreased, in both the mutant and wild-type strain, suggesting that this form of NPQ reflects the operation of CCM in certain conditions. Possible candidates for the RPR mutation and the relationship between CCM and photosynthetic electron flow are discussed.Key words: Chlamydomonas reinhardtii, chlorophyll fluorescence, CO2-concentrating mechanism, low-CO2 responsive gene, phosphoglycolate phosphatase, photorespiration.

scholarly journals Bi-directional electron transfer between H2 and NADPH mitigates light fluctuation responses in green algae

2021 ◽  
Author(s):  
Yuval Milrad ◽  
Shira Schweitzer ◽  
Yael Feldman ◽  
Iftach Yacoby
Keyword(s):  
Green Algae ◽  
Fossil Fuels ◽  
Electron Flow ◽  
Scale Up ◽  
Photosynthetic Apparatus ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Redox Balance ◽  
Promising Alternative ◽  
Photosynthetic Organisms ◽  
Nadph Metabolism

Abstract The metabolism of green algae has been the focus of much research over the last century. These photosynthetic organisms can thrive under various conditions and adapt quickly to changing environments by concomitant usage of several metabolic apparatuses. The main electron coordinator in their chloroplasts, nicotinamide adenine dinucleotide phosphate (NADPH), participates in many enzymatic activities and is also responsible for inter-organellar communication. Under anaerobic conditions, green algae also accumulate molecular hydrogen (H2), a promising alternative for fossil fuels. However, to scale-up its accumulation, a firm understanding of its integration in the photosynthetic apparatus is still required. While it is generally accepted that NADPH metabolism correlates to H2 accumulation, the mechanism of this collaboration is still vague and relies on indirect measurements. Here, we investigated this connection in Chlamydomonas reinhardtii using simultaneous measurements of both dissolved gases concentration, NADPH fluorescence and electrochromic shifts at 520-546 nm. Our results indicate that energy transfer between H2 and NADPH is bi-directional and crucial for the maintenance of redox balance under light fluctuations. At light onset, NADPH consumption initially eventuates in H2 evolution, which initiates the photosynthetic electron flow. Later on, as illumination continues the majority of NADPH is diverted to the Calvin-Benson-Bassham cycle. Dark onset triggers re-assimilation of H2, which produces NADPH and so, enables initiation of dark fermentative metabolism.

scholarly journals Bi-directional electron transfer between H2 and NADPH mitigates the response to light fluctuations in green algae

2020 ◽  
Author(s):  
Yuval Milrad ◽  
Shira Schweitzer ◽  
Yael Feldman ◽  
Iftach Yacoby
Keyword(s):  
Energy Transfer ◽  
Green Algae ◽  
Fossil Fuels ◽  
Electron Flow ◽  
Scale Up ◽  
Photosynthetic Apparatus ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Redox Balance ◽  
Promising Alternative ◽  
Light Fluctuations

AbstractThe metabolism of green algae has been the focus of much research over the last century. These photosynthetic organisms can thrive under various conditions and adapt quickly to changing environments by concomitant usage of several metabolic apparatuses. The main electron coordinator in their chloroplasts, nicotinamide adenine dinucleotide phosphate (NADPH), participates in many enzymatic activities and is also responsible for interorganelle communication. Under anaerobic conditions, green algae also accumulate molecular hydrogen (H2), a promising alternative for fossil fuels. However, in order to scale-up its accumulation, a firm understanding of its integration in the photosynthetic apparatus is still lacking. While it is generally accepted that NADPH metabolism correlates to H2 accumulation, the mechanism of this collaboration is still vague and rely on indirect measurements. Here, we investigated this connection using simultaneous measurements of both dissolved gases concentration, NADPH fluorescence and electrochromic shifts at 520-546 nm. Our results indicate that energy transfer between H2 and NADPH is bi-directional and crucial for the maintenance of redox balance under light fluctuations. At light onset, NADPH consumption is initially eventuated in H2 evolution, which initiate the photosynthetic electron flow. Later on, as illumination continues the majority of NADPH is recycled by Nda2 rather than consumed by terminal sinks such as CBB cycle and H2 production. Dark onset triggers re-assimilation of H2, which produces NADPH and so, enables initiation of dark fermentative metabolism.One sentence summaryEnergy transfer between H2 and NADPH is bi-directional and crucial for the maintenance of redox balance under light fluctuations.

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