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X-Nuclei MRI and Energy Metabolism
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
Link reaction process: Processing pyruvate to acetyl CoA. The link reaction, also called pyruvate oxidation or pyruvate decarboxylation, is an important link between glycolysis, which produces 3-carbon molecule pyruvate, and the TCA cycle, which starts with 2-carbon molecule acetyl CoA. The link reaction can be summarized in the following steps: Pyruvate is first transported inside the mitochondrion matrix.Pyruvate is then processed inside the 3-enzyme complex pyruvate dehydrogenase: one of its carbons is oxidized to CO2 and resulting in a 2-carbon acetyl unit, NAD+ is reduced to NADH + H+, and finally the acetyl unit is transferred to CoA to produce acetyl CoA.
Bioinspired Nanomaterials for Improving Sensing and Imaging Spectroscopy
Published in Kaushik Pal, Nanomaterials for Spectroscopic Applications, 2021
Janti Qar, Alaa A. A. Aljabali, Tasnim Al-Zanati, Mazhar S. Al Zoubi, Khalid M. Al-Batanyeh, Poonam Negi, Gaurav Gupta, Dinesh M. Pardhi, Kamal Dua, Murtaza M. Tambuwala
E2 is derived from the pyruvate-dehydrogenase-multienzyme complex’s E2 central domain (dihydrolipoamide acetyltransferase). The protein consists of 24 subunits in E. coli or 60 subunits Geobacillus stearothermophilus that self-assembly into a hollow system of a cubic central core, or an icosahedron with 12 pores of five nm openings [33]. Pyruvate decarboxylase (E1), dihydrolipoamide acetyltransferase (E2), and dihydrolipoamide dehydrogenase are the enzymes that are unique to pyruvate dehydrogenase (E3). Because the E1 and E3 are not separated, the latter shapes the systemic nucleus of inherent durability in the presence of the E2, which enables long-term survival under harsh environments. The modulation of the exterior surface with functional ligands does not inhibit the assembly of the core domain E2, as is the case with other nanocages, including viral capsids. This function is the same as its natural condition in which the E2 domain is linked to two distinct folding protein domains on its top [33]. E2 protein nanocage can be genetically or chemically engineered in a similar way to other natural protein (viruses) to enable multiple functions such as drug loading and precise delivery. Ren et al. have shown that
The Sustainable Production of Polyhydroxyalkanoates from Crude Glycerol
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Neha Rani Bhagat, Preeti Kumari, Arup Giri, Geeta Gahlawat
The first pathway for PHA synthesis from glycerol involves the combination of the glycolytic pathway and the TCA cycle. Here, glycerol is broken down into dihydroxyacetone (DHA) and glycerol-3-phosphate (G3P) with the help of the enzymes glycerol dehydrogenase (DhaD) and glycerol kinase (GlpK). These two molecules are then broken down into DHAP by the enzymes dihydroxyacetone kinase (DhaK) and glycerol 3-phosphate dehydrogenase [28]. This DHAP molecule is then converted into pyruvate via the glycolysis pathway. Furthermore, through the pyruvate dehydrogenase reaction, pyruvate is converted into acetyl-CoA in the presence of coenzyme A with the release of a CO2 molecule and reduction of NAD+ into NADH. Acetyl-CoA is the major intermediate molecule that further participates in the TCA cycle to form the next substrate, namely succinyl-CoA. Succinyl-CoA is then converted into succinate semialdehyde by the enzyme succinate semialdehyde dehydrogenase (SucD) [44]. Furthermore, succinate semialdehyde is converted into 4-hydroxybutyrate and 4-hydroxybutyryl-CoA via 4-hydroxybutyrate dehydrogenase (4hbD) and 4-hydroxybutyrate-CoA: CoA transferase (OrfZ) [44,45]. This formation of either HA-CoA or HB-CoA is considered as a major step in PHA synthesis where these end molecules get polymerized into scl-PHA molecules via PHA synthase enzymes.
Effects of glycerol and glucose on docosahexaenoic acid synthesis in Aurantiochyrium limacinum SFD-1502 by transcriptome analysis
Published in Preparative Biochemistry & Biotechnology, 2023
Huaqiu Zhang, Xiangying Zhao, Chen Zhao, Jiaxiang Zhang, Yang Liu, Mingjing Yao, Jianjun Liu
Pyruvate is synthesized in the cytoplasm, and then enters the mitochondria. Under the catalysis of pyruvate dehydrogenase (PDH), pyruvate decarboxylates into acetyl-CoA, which enters the TCA pathway. The transcriptome data showed that the expression of PDH in glucose group cultured for 24 hr was twice as high as that in glycerol group. Compared with glycerol, isocitrate dehydrogenase (ICDH), fumarase, malate dehydrogenase (MDH) which participate in tricarboxylic acid cycle, were upregulated in glucose by 1.65-fold, 1.46-fold, 6.02-fold, respectively. At 48 and 72 hr, only the expression of MDH in glucose group is higher than that of glycerol (2.76- and 2.55- times), the expression of PDH and ICDH is similar. Meanwhile, in glucose group, the expression levels of PDH, ICDH and MDH at 24 hr were higher than those at 48 hr. However, the expression of glycerol group in 24 hr was lower than that in 48 hr, which indicated that the oxidative decarboxylation of acetyl-CoA into TCA pathway was catalyzed by pyruvate dehydrogenase (PDH), and the TCA cycle of cells with glucose as the carbon source was earlier than that of cells with glycerol as carbon source.
Arsenic exposure from groundwater: environmental contamination, human health effects, and sustainable solutions
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Elida Cristina Monteiro De Oliveira, Evelyn Siqueira Caixeta, Vanessa Santana Vieira Santos, Boscolli Barbosa Pereira
In the human body, arsenite binds to thiol groups found in proteins of different tissues, including lung, spleen, liver, kidneys, and gastrointestinal mucosa, and this metalloid may be harmful even at low concentrations. Further, arsenite inhibits pyruvate dehydrogenase (PDH) complex through interaction with the active form of lipoic acid, lipoamide, thereby interfering with cellular energy metabolism (Costa 2019). The toxicity of arsenate is triggered by the inactivation of several enzymes, especially those related to DNA synthesis and repair, and in the production of energy for cells (Souza et al. 2019). Recently, Chang and Singh (2019) investigated As-induced carcinogenicity in renal epithelial cells and found no significant effects on cell growth rate following acute72 hr treatment.
Effects of mixotrophic cultivation on antioxidation and lipid accumulation of Chlorella vulgaris in wastewater treatment
Published in International Journal of Phytoremediation, 2020
Ran Li, Jie Pan, Minmin Yan, Jiang Yang, Wenlong Qin
The fatty acid synthesis pathway of mixotrophic C. vulgaris in wastewater is illustrated in Figure 5. Specifically, CO2 enters the chloroplast to produce glyceraldehyde triphosphate through the Calvin cycle. After that, the glycolytic pathway forms pyruvate, which releases a CO2 molecule and produces acetyl-CoA under the action of pyruvate dehydrogenase (PDH) (Avidan et al.2015). The first key reaction in fatty acid synthesis is the acetyl-CoA conversion to malonyl-CoA catalyzed by ACCase. Our results showed the ACCase activity was enhanced and contributed to the fatty acid accumulation of C. vulgaris cultured in wastewater. During heterotrophic metabolism, after a small molecule of organic matter (e.g., glucose) enters the cell, it is first converted to pyruvic acid by the glycolysis pathway and then by the fatty acid metabolism pathway (Gao et al.2014). Glucose can also be converted into ADPGlc and then into starch under the catalysis by AGPase. However, the activity of ACCase in mixotrophic C. vulgaris in wastewater was weakened, indicating more glucose molecules participate in fatty acid synthesis, causing lipid accumulation.