China
Africa
Explore chapters and articles related to this topic
Biogeneration of Volatile Organic Compounds in Microalgae-Based Systems
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Pricila Nass Pinheiro, Karem Rodrigues Vieira, Andriéli Borges Santos, Eduardo Jacob-Lopes, Leila Queiroz Zepka
In general, microalgae are commonly grown by converting dissolved, inorganic carbon (CO2) and absorbing solar energy. They have pigments such as chlorophyll and carotenoids, and in some cases phycobiliproteins which are involved in capturing luminous energy to perform photosynthesis. For the CO2 converted into carbohydrates, catalyzed by the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), this process is referred to as the Calvin cycle. The Calvin cycle is the metabolic mechanism for fixing CO2 in microalgae. This process comprises three stages; carboxylation, reduction, and regeneration. The end of the cycle forms one molecule of glyceraldehyde-3-phosphate that through the action of enzymes forms phosphoenolpyruvate, and finally pyruvate (Santos et al. 2016a).
Anatomy, Biochemistry and Physiology
Published in Massimo Maffei, Vetiveria, 2002
Cinzia M. Bertea, Wanda Camusso
Preliminary studies on the photosynthetic apparatus provided localization of the key enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) exclusively in bundle sheath cells (Giaccone et al., 1990, 1991) as reported before.
Introduction
Published in René Lontie, Copper Proteins and Copper Enzymes, 1984
Copper does not seem essential for some enzymes, which have been claimed to contain this metal. A crystalline preparation of ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) from tobacco did not seem to contain appreciable amounts of copper,33 in contrast with an earlier report on a preparation from spinach.34 With parsley the ribulose 1,5-bisphosphate oxygenase seemed a separate enzyme, which contained copper.35 Indoleamine 2,3-dioxy-genase did not contain significant amounts of copper, as a copper-rich protein was eliminated in the last step of the purification.36 With L-tryptophan 2,3-dioxygenase (EC 1.13.11.11) of Pseudomonas acidovorans, which contains protoheme IX, it was shown that copper was not essential for the catalytic activity, although some preparations contained firmly bound copper.37
Functional signatures of ex-vivo dental caries onset
Published in Journal of Oral Microbiology, 2022
Dina G. Moussa, Ashok K. Sharma, Tamer A Mansour, Bruce Witthuhn, Jorge Perdigão, Joel D. Rudney, Conrado Aparicio, Andres Gomez
The upregulation of some metabolites along the glycolysis pathways is self-explanatory based on the fermentation of carbohydrates induced by bacterial metabolism. However, the depletion of Fumarate was an interesting finding that triggered our curiosity (Figure 7and Table 1). Fischbach and Sonnenburg systematically explained this phenomenon in the context of how anaerobic bacteria generate energy (ATP), maintain redox balance, and acquire carbon and nitrogen to synthesize primary metabolites [92]. They elucidated how Fumarate is key for anaerobic ATP synthesis in the final step of the primitive electron transport chain through its reduction to succinate, pointing to this metabolite as the most common terminal electron acceptor for anaerobic respiration [93]. Since biofilms were grown in an aerobic environment, as it happens with supragingival plaque in-vivo, excessive Fumarate consumption could be attributed to the presence of some strict anaerobic species within the microbial community – such as Veillonella (in WS_T1 and T2) and Fusobacterium (in WS_T2) – which strive to maintain their survival and energy production as aforementioned. Intriguingly, Ribulose-5-phosphate, also showed significant depletion at a later stage, when the lesions became overt (Figure 7and Table 1). The mechanisms behind depletion of this metabolite are unclear; however, ribulose-1,5-bisphosphate – the product of the phosphorylation of ribulose-5-phosphate- has been found to be the most important CO2 fixing pathway in prokaryotes, particularly around oxic/anoxic (free oxygen containing/free oxygen lacking) interfaces [94] that develop as a consequence of oxygen consumption [95]. Collectively, Ribulose-5-phosphate consumption seems to be also involved in bacterial adaptation mechanisms used for managing CO2 deficiency at an advanced stage of biofilm maturations.
Use of an immobilised thermostable α-CA (SspCA) for enhancing the metabolic efficiency of the freshwater green microalga Chlorella sorokiniana
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Giovanna Salbitani, Sonia Del Prete, Francesco Bolinesi, Olga Mangoni, Viviana De Luca, Vincenzo Carginale, William A. Donald, Claudiu T. Supuran, Simona Carfagna, Clemente Capasso
Photosynthesis employs sunlight and the reaction between CO2 and H2O to generate carbohydrates and oxygen as a side product. This gas is necessary for the aerobic respiration but also promotes the formation of the ozone layer in the upper atmosphere. During the photosynthetic reactions, the energy of sunlight is converted into chemical energy, i.e., ATP and NADPH, which are thereafter involved in the biosynthesis of carbohydrates from CO2 as a unique carbon source1,2. The aerobic respiration (glucose + O2 → H2O + CO2), on the contrary, is the process of energy production, which converts sugars into carbon dioxide and water. These two opposite reactions influence the global carbon cycle, being fundamental for most life forms on earth2. The light-dependent reactions to form glucose and other carbohydrates are known as the Calvin-Benson cycle. There are three photosynthetic pathways, C3, C4, and CAM (Crassulacean Acid Metabolism) that exist among terrestrial plants3,4. In the C3 photosynthesis, which is the most ancestral form, the enzyme ribulose bisphosphate carboxylase-oxygenase (RuBisCO)5, which is present in the chloroplast stroma of C3 plants, combines the ribulose-1,5-bisphosphate (RuBP), a molecule containing five carbon atoms, with CO2 to form two molecules of phosphoglycerate (PGA, a 3-carbon molecule)6,7. In the C4 pathway, the CO2 is converted into bicarbonate, which is subsequently reacted with phosphoenolpyruvic acid (PEP), a 3-carbon molecule, in the presence of phosphoenolpyruvate carboxylase (PEPC)8. The product of this reaction is a 4-carbon molecule, oxaloacetic acid (OAA), which is thereafter reduced to malate, another four-carbon acid8. The CAM pathway was documented for the first time in plant families that are adapted to very arid regions, such as many epiphytes and succulents9. These plants have a dual pathway of carboxylation temporally separated into the same tissue. In the night with the stomata opening, the CO2 is fixed as an organic acid form of the anion malate by PEPC. In contrast, during the day, with the stomatal closure, the malic acid undergoes decarboxylation, determining an increase of CO2 around the enzyme RuBisCO of about 60 times the ambient levels, allowing the photosynthetic reaction typical of the C3 cycle mentioned above9. The RuBisCO enzyme also uses O2 as substrate, not only CO210. The rate of the oxygenation and carboxylation by RuBisCO is controlled by the levels of O2 and CO2 and is the primary factor in determining the efficiency of the photosynthetic process11. CAM is one example of a carbon-concentrating mechanism (CCM) in higher order plants, in which, as mentioned above, decarboxylation of malic acids affords supplementary amounts of CO2.