Effects of Photoinhibition on Photosynthetic Carbon Metabolism in Intact Isolated Spinach Chloroplasts.

1987 ◽  
Vol 14 (4) ◽  
pp. 439 ◽  
Author(s):  
C Giersch ◽  
SP Robinson
Keyword(s):  
Carbon Flux ◽  
Co2 Fixation ◽  
Calvin Cycle ◽  
Chloroplast Envelope ◽  
Low Light ◽  
Spinach Chloroplasts ◽  
Fructose 1,6 Bisphosphatase ◽  
Photosynthetic Carbon Metabolism ◽  
Chloroplast Stroma ◽  
Fructose 1,6 Bisphosphate

Pools of intermediates of the Calvin cycle were measured during photosynthetic 14CO2 fixation by intact isolated spinach chloroplasts. Photoinhibitibn (illumination for 8 min with 4000 �mol m-2 s-1 light in the absence of bicarbonate) decreased the subsequently measured rate of CO2 fixation. Individual compounds were differently affected: the ribulose-1,5-bisphosphate (RuBP) pool was drastically lowered, while that of fructose-1,6-bisphosphate (FBP) was increased, suggesting that photoinhibition causes a limitation in RuBP regeneration. An increase in FBP and decrease in RuBP were not observed during photosynthesis in low light at rates of CO2 fixation comparable to those in photoinhibited chloroplasts. This indicates that changes of the metabolite pools induced by photoinhibition were not due solely to decreased rates of electron transport. Activities of RuBP carboxylase and fructose-1,6-bisphosphatase (FBPase) were decreased by the photoinhibitory treatment. However, the activity of both enzymes in photoinhibited chloroplasts was still well in excess of that required to sustain the measured rates of carbon flux. Photoinhibition largely abolished the light-induced proton gradient across the chloroplast envelope. The concomitant acidification of the chloroplast stroma could inhibit FBPase activity. It is concluded that photoinhibition does not result in irreversible modification of the FBPase protein but that its activity may be decreased by changes in pH and possibly other factors in the chloroplast stroma.

Regulation of Fructose 1,6-Bisphosphatase Activity of Chlorella by Mole Mass Change

1996 ◽  
Vol 51 (9-10) ◽  
pp. 639-645 ◽  
Author(s):  
N. Grotjohann
Keyword(s):  
Enzyme Regulation ◽  
Fold Increase ◽  
Substrate Affinity ◽  
Kinetic Properties ◽  
Enzyme Form ◽  
Phosphorylated Compounds ◽  
Fructose 1,6 Bisphosphatase ◽  
Chloroplast Stroma ◽  
Fructose 1,6 Bisphosphate

Fast protein liquid chromatography on Superose 6 of partially purified FBPase II from Chlorella reveals a 1350 kDa-form at pH 6.0 and a 67 kDa-form at pH 8.5. Treatment of the large enzyme form with 5mᴍ concentrations of Mg2+, F1,6P2, DTT or ATP leads to dissociation into smaller ones of 215 -470 kDa. Aggregation/dissoziation is a reversible process, as has been shown for the effect of F1,6P2 and of pH, by rechromatography. The change in mole mass results in alterations of the activitiy and of the kinetic properties of the enzyme forms, obtained. Dissociation results in a 4 - 6 fold increase in activity, as can be shown for F1,6P2-treated samples. Halfsaturation constants, as well as the degree of cooperativity of the 67- and the 1350- kDa form, are different for substrate affinity, activation by Mg2+ and DTT, and for inhibition by ATP. Both enzyme forms hydrolyse fructose 1,6 bisphosphate and seduheptulose 1,7 bisphosphate better than other phosphorylated compounds. The ratio of F1,6P2- to SDP-cleavage is 100:58 for the small enzyme form and 100: 84 for the large one. Activation of FBPase II in the light and inactivation in the dark is discussed on the basis of different oligomeric forms of the enzyme, generated by changes in the concentration of intermediates and effectors in the chloroplast stroma, leading to dissociation or aggregation. The conclusion is drawn that oligomerization of key enzymes, resulting in enzyme forms with different activities and different kinetic properties, might provide an effective mechanism for enzyme regulation in vivo

scholarly journals Action of calcium ions on spinach (Spinacia oleracea) chloroplast fructose bisphosphatase and other enzymes of the Calvin cycle

1980 ◽  
Vol 188 (3) ◽  
pp. 775-779 ◽  
Author(s):  
S A Charles ◽  
B Halliwell
Keyword(s):  
Calcium Ions ◽  
Spinacia Oleracea ◽  
Calvin Cycle ◽  
Complete Inhibition ◽  
Fructose Bisphosphatase ◽  
Spinach Chloroplasts ◽  
Fructose 1,6 Bisphosphate ◽  
Sedoheptulose Bisphosphatase

Thiol-treated spinach (Spinacia oleracea) chloroplast fructose bisphosphatase is powerfully inhibited by Ca2+ non-competitively with respect to its substrate, fructose 1,6-bisphosphate. 500 microM-Ca2+ causes virtually complete inhibition and the Ki is 40 microM. Severe inhibition of sedoheptulose bisphosphatase is also caused by Ca2+. A role for Ca2+ in regulation of the Calvin cycle in spinach chloroplasts is proposed.

scholarly journals On the Activation of Fructose-1,6-bisphosphatase of Spinach Chloroplasts and the Regulation of the Calvin Cycle

1981 ◽  
Vol 113 (3) ◽  
pp. 507-511 ◽  
Author(s):  
Jacques PRADEL ◽  
Jean-Michel SOULIE ◽  
Jean BUC ◽  
Jean-Claude MEUNIER ◽  
Jacques RICARD
Keyword(s):  
Calvin Cycle ◽  
Spinach Chloroplasts ◽  
Fructose 1,6 Bisphosphatase

scholarly journals Why an increase in activity of an enzyme in the Calvin Benson Cycle does not always lead to an increased photosynthetic CO2 uptake rate? – A theoretical analysis

2020 ◽  
Author(s):  
Honglong Zhao ◽  
Qiming Tang ◽  
Tiangen Chang ◽  
Yi Xiao ◽  
Xin-Guang Zhu
Keyword(s):  
Reaction Rates ◽  
Initial Increase ◽  
Co2 Uptake ◽  
Systems Model ◽  
Low Concentrations ◽  
Fructose 1,6 Bisphosphatase ◽  
Photosynthetic Carbon Metabolism ◽  
Fructose 1,6 Bisphosphate ◽  
Developmental Conditions ◽  
Control Coefficients

Abstract Overexpressing Calvin Benson cycle (CBC) enzyme shown to limit the flow of CO2 through the cycle is a major approach to improve photosynthesis. Though control coefficients of CBC enzymes vary under different environmental and developmental conditions, it is usually implicitly assumed that enzymes in the CBC have a monotonic impact on the CBC fluxes. Here, with a dynamic systems model of the photosynthetic carbon metabolism, we show that, for glycerate-3-phosphate kinase (PGAK), fructose-1,6-bisphosphatase (FBPase), fructose-1,6-bisphosphate aldolase (FBA) and transketolase (TKa), individually increasing activity of these CBC enzymes theoretically leads to an initial increase then decrease in the fluxes through the CBC. Also, the inhibition constants of ADP for PGAK and of F6P for FBPase influence the CBC flux in a biphasic manner. These predicted enzymes showing a biphasic manner are always located in different sub-cycles of the CBC, which consume the shared substrates in the early steps in the CBC and produce intermediates used as substrates for enzymes in the later reactions. We show that the excessive increase in activities of enzymes in one sub-cycle consuming the shared metabolite could cause low concentrations of metabolites in the other sub-cycles, which results in low reaction rates of the later reactions and hence lowers overall CBC flux. This study provides a model to explain the underlying reasons that overexpression of enzymes in the CBC sometimes can negatively impact photosynthesis. We find that balanced activities of enzymes in the sub-cycles of the CBC are required to gain a higher efficiency of the CBC.

scholarly journals Low Light Alters the Photosynthesis Process in Cigar Tobacco via Modulation of the Chlorophyll Content, Chlorophyll Fluorescence, and Gene Expression

Agriculture ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 755
Author(s):  
Xiaoying Wu ◽  
Rayyan Khan ◽  
Huajun Gao ◽  
Haobao Liu ◽  
Juan Zhang ◽  
...  
Keyword(s):  
Chlorophyll Content ◽  
Co2 Fixation ◽  
Calvin Cycle ◽  
Enzyme Synthesis ◽  
Light Interception ◽  
Carbon Utilization ◽  
Low Light ◽  
Tobacco Production ◽  
Cultivation Technique ◽  
Rbcs Genes

Shading or low light (LL) conditions are a key and necessary cultivation technique in cigar wrapper tobacco production. However, the effect of low light on the photosynthesis in cigar tobacco is not clear. Therefore, this study is designed to know the photosynthesis of cigar tobacco under different light intensities (T200, T100, and T50 μmol m−2 s−1). The results reveal that under low light, T50 especially improved the light interception and increased carbon utilization, as witnessed by a higher specific leaf area and lower specific leaf weight. Low light intensity caused better light interception and carbon utilization in cigar tobacco leaves, and thus thinner leaves are more able to use low light efficiently. The chlorophyll content is related to the photosynthesis process; thus, LL affected the photosynthesis process by lowering the chlorophyll content. Similarly, LL also altered the photosynthetic efficiency by lowering the QY_Lss, qP_Lss, and Rfd_Lss. Additionally, higher expression of Lhcb4.2, Lhcb6, PsbA, PsbB, and PsbD under low light, especially T50, shows that the PSII and antenna proteins complex efficiently utilized the absorbed energy for photosynthesis. Finally, the lower photosynthesis, particularly in T50, is attributed to the downregulation of genes related to NADPH production (petH) and the rubisco enzyme synthesis-related gene (rbcs) for CO2 fixation in the Calvin cycle. Overall, the results show that the photosynthesis is decreased under LL intensities which might be related to lower chlorophyll content and downregulation of petH and rbcs genes.

Chloroplast Autonomy in Acetyl-Coenzyme-A-Formation and Terpenoid Biosynthesis

1980 ◽  
Vol 35 (7-8) ◽  
pp. 645-648 ◽  
Author(s):  
K. H. Grumbach ◽  
B. Forn
Keyword(s):  
Coenzyme A ◽  
Calvin Cycle ◽  
Mevalonic Acid ◽  
Carbon Flow ◽  
Chloroplast Envelope ◽  
Terpenoid Biosynthesis ◽  
Acetyl Coenzyme A ◽  
Spinach Chloroplasts ◽  
Acetyl Coenzyme ◽  
Β Carotene

Abstract Isolated intact spinach chloroplasts were supplied with 14C-labeled CO2, phosphoglycerate, phos-phoenolpyruvate, acetate and mevalonate and the incorporation of radioactivity into β-carotene and plastoquinone-9 assayed. All applied substrates were capable of crossing the chloroplast envelope. Except phosphoenolpyruvate all radioactive precursors were incorporated into β-carotene and also into plastoquinone-9. It is concluded that spinach chloroplasts are autonom in acetyl-coenzyme-A-formation and terpenoid biosynthesis. There is a direct carbon flow from intermediates of the Calvin-cycle via acetyl-coenzyme-A and mevalonic acid existing in the chlo­ roplast leading to the carotenoids and isoprenoid side-chains of chlorophylls and quinones.

Microsequecing and cDNA cloning of the Calvin cycle/OPPP enzyme ribose-5-phosphate isomerase (EC 5.3.1.6) from spinach chloroplasts

1996 ◽  
Vol 30 (4) ◽  
pp. 795-805 ◽  
Author(s):  
William Martin ◽  
Katrin Henze ◽  
Josef Kellermann ◽  
Anke Flechner ◽  
Claus Schnarrenberger
Keyword(s):  
Cdna Cloning ◽  
Calvin Cycle ◽  
Spinach Chloroplasts

Substrate-Binding Isotherms of Spinach Chloroplastic Fructose-1,6-bisphosphatase and the Photoregulation of the Calvin Cycle

1981 ◽  
Vol 113 (3) ◽  
pp. 513-520 ◽  
Author(s):  
Jean-Claude MEUNIER ◽  
Jean BUC ◽  
Jean-Michel SOULIE ◽  
Jacques PRADEL ◽  
Jacques RICARD
Keyword(s):  
Substrate Binding ◽  
Calvin Cycle ◽  
Binding Isotherms ◽  
Fructose 1,6 Bisphosphatase

Structure of the chloroplast and its DNA in chloromonadophycean algae

1981 ◽  
Vol 49 (1) ◽  
pp. 401-409
Author(s):  
A.W. Coleman ◽  
P. Heywood
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Membrane ◽  
Nuclear Envelope ◽  
Chloroplast Dna ◽  
Single Layer ◽  
Longitudinal Axis ◽  
Chloroplast Envelope ◽  
Large Numbers ◽  
Gonyostomum Semen ◽  
Chloroplast Stroma

The arrangement and ultrastructure of chloroplasts is described for the Chloromonadophycean algae gonyostomum semen Diesing and Vacuolaria virescens Cienkowsky. The chloroplasts are present in large numbers and are discoid structures approximately 3–4 micrometer in length by 2–3 micrometer in width. In Gonyostomum semen the chloroplasts form a single layer immediately interior to the cell membrane; frequently their longitudinal axis parallels the longitudinal axis of the cell. The chloroplasts in Vacuolaria virescens are more than I layer deep and do not appear to be preferentially oriented. In both organisms, chloroplast bands usually consist of 3 apposed thylakoids, although fusion and interconnections between adjacent bands frequently occur. External to the girdle band (the outermost thylakoids) is the chloroplast envelope. This is bounded by endoplasmic reticulum but there is no immediately apparent continuity between this endoplasmic reticulum and the nuclear envelope. Electron-dense spheres in the chloroplast stroma are thought to be lipid food reserve. Ring-shaped electron-translucent regions in the chloroplast contain chloroplast DNA. The DNA is distributed along this ring in an uneven fashion and, when stained, resembles a string of beads. Each plastid has I ring, and the ring is unbroken in the intact plastid.

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