Biogeneration of Volatile Organic Compounds in Microalgae-Based Systems
Gokare A. Ravishankar, Ranga Rao Ambati in Handbook of Algal Technologies and Phytochemicals, 2019
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).
Ascorbic Acid
Ruth G. Alscher, John L. Hess in Antioxidants in Higher Plants, 2017
Oxygen competes with NADP for reducing equivalents (Figure 7). Electron flow to oxygen has always been considered to be rather low under steady-state conditions, accounting for less than 20% of the net steady-state rate of oxygen evolution during CO2 assimilation at high irradiances.87,88 However, when CO2 assimilation is restricted and the NADP pool becomes relatively reduced, electron flow to O2 is favored. Such a situation arises during the induction phase of photosynthesis that follows a transition from darkness to light or a transition from low irradiance to high irradiance.89-92 In this situation, over-reduction is necessary to force the thiol-dependent activation of the light-modulated enzymes of the Benson-Calvin cycle.90 During the induction phase, the processes of psudocyclic and cyclic electron flow serve to generate ATP because noncyclic electron flow is limited by the availability of NADP.90 Once the thiol-modulated enzymes of the Benson-Calvin cycle are activated, the turnover of this cycle increases the demand for NADPH, and ATP also increases such that the NADPH to NADP ratio falls to a level very close to the dark value, and noncyclic electron flow is predominant.90
Biotechnological Studies of Medicinal Plants to Enhance Production of Secondary Metabolites under Environmental Pollution
Azamal Husen in Environmental Pollution and Medicinal Plants, 2022
Being immobile, plants constantly interact with the rapidly changing and potentially damaging climate change. Thus, to counteract the effect, plants have evolved various complex defence mechanisms involving the synthesis of a diverse range of chemical metabolites which play a major role in the adaptation of plants (Holopainen and Gershenzon 2010). Although secondary metabolites have different structures and functions, they originate from the intermediate products of primary metabolism. For example, phenylalanine, the precursor of phenylpropanoid metabolism, is produced from the intermediate product (erythrose-4-phosphate) of the Calvin cycle and pentose phosphate pathway (Caretto et al. 2015).
Purification and characterisation of glutathione reductase from scorpionfish (scorpaena porcus) and investigation of heavy metal ions inhibition
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Glutathione reductase (EC 1.8.1.7; GR), a major enzyme in glutathione metabolism, is required for the maintenance of the reduced form of cellular glutathione, which is strongly nucleophilic for many reactive electrophiles10,11. The flavin enzyme GR acts as an antioxidant to protect cells from oxidative stress by reducing glutathione disulphide (GSSG) to its reduced form (GSH)12. It has an important role in the drug and detoxification mechanisms especially in the liver. This is due to the cytochrome P-450 system found in liver microsomes, which provides detoxifying events13. Maintaining the GSH/GSSG ratio in the cell environment is one of the most important known targets of the GR enzyme-catalysed reactions14. Glutathione reductase is involved in the reduction-oxidation of intracellular glutathione for GSSG, which is generated through the detoxification of hydroperoxides and reduction of some other chemicals catalysed by glutathione perdoxidase15. The NADP+ dependent malate dehydrogenase and pentose phosphate pathways provide the NADPH needed in this catalytic process16,17. NADPH, a key product of the pentose phosphate cycle, is employed extensively in reductive biosynthesis. Furthermore, it aids in the protection of the cell against oxidative damage9.
Cognitive function improvement after fecal microbiota transplantation in Alzheimer’s dementia patient: a case report
Published in Current Medical Research and Opinion, 2021
Soo-Hyun Park, Jung Hwan Lee, Jongbeom Shin, Jun-Seob Kim, Boram Cha, Suhjoon Lee, Kye Sook Kwon, Yong Woon Shin, Seong Hye Choi
Functional biomarker analysis using the Kruskal-Wallis H test was performed between the pre- and post-FMT groups by using EzBio-Cloud Apps (ChunLab Inc., Seoul, Korea). Pentose phosphate cycle, the functional pathway associated with the production of SCFA, was found to be significantly different between before and after FMT (p = .026)17.
Still challenging: the ecological function of the cyanobacterial toxin microcystin – What we know so far
Published in Toxin Reviews, 2018
Azam Omidi, Maranda Esterhuizen-Londt, Stephan Pflugmacher
The hypothesized involvement of MCs in photosynthesis was further supported by studies using an immunogold-labeling technique that disclosed that the thylakoids membrane is the most MC-occupied cell site followed by the nucleoplasmic area. Physically, more than two-thirds of MCs were attached to the thylakoids membranes (Shi et al., 1995; Young et al., 2005,2008). Although a further study using the cryofixation/cryosectioning technique demonstrated that most of the MCs were localized in the nucleoplasmic area and intracellular inclusions such as carboxysomes and polyphosphate bodies, rather than thylakoids membranes and the cell wall (Gerbersdorf, 2006). Under high light irradiation, the ratio of MCs in outer to inner cellular parts increased, and a higher percentage of MCs were found close to the thylakoids membrane suggesting the probable role of MCs in light adaptation (Gerbersdorf, 2006). Moreover, the M. aeruginosa mcyA-knockout mutant has been found to be dominant under low light, with the toxic genotype M. aeruginosa PCC 7806 showing a greater fitness to high light suggesting that MCs play a role in protection against photooxidation (Phelan & Downing, 2011). In contrast, another study showed that under both low and high light irradiation (1480 and 5920 lm m−2, respectively) a mixed culture was dominated by the MC-producing strain M. aeruginosa UTCC 300 which further emphasized the importance of MCs in light adaptation (Renaud et al., 2011). Comparative proteomic studies also revealed two NADPH-dependent reductases, phycobiliproteins, and RuBisCo, which is a Calvin cycle enzyme, were expressed differently in the wild-type and mcyB− mutant of M. aeruginosa PCC 7806. Furthermore, MC-protein binding was significantly enhanced under high light (51 800 lm m−2) which was assumed to increase the protein stability and avoid redox changes (Zilliges et al., 2011). Therefore, the potential role of MCs in photooxidative protection under high light is an advantage for the organism (Gerbersdorf, 2006; Phelan & Downing, 2011). In another study with M. aeruginosa PCC7806 and its MC-deficient mutant, differences in metabolic responses between strains upon exposing to high light intensity (18 500 lm m−2) were observed. Trehalose and sucrose, two general stress markers, accumulated more in the mutant while carbon reserves such as glycolate accumulated faster in the wild type. Additionally, the photosynthesis rate and high molecular weight carbohydrate contents were greater in the wild type (Meissner et al., 2015).
Related Knowledge Centers
- Carbon Dioxide
- Chloroplast
- Glucose
- Nicotinamide Adenine Dinucleotide Phosphate
- Phloem
- Photosynthesis
- Stroma
- Sucrose
- Thylakoid
- Adenosine Triphosphate