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Environmentally Friendly Approach: Synthesis and Biological Evaluation of α-Aminophosphonate Derivatives
Published in Satish A. Dake, Ravindra S. Shinde, Suresh C. Ameta, A. K. Haghi, Green Chemistry and Sustainable Technology, 2020
Nature has chosen phosphates as essential chemicals in many critically important biological processes and materials. They are so versatile and fundamentally important in the chemistry of living systems, in many ways, that it would be difficult to imagine any other chemical types would be able to meet the manifold demands of living systems [19]. The phosphate group is present in (i) intermediates of important biochemical pathways (e.g., sugar phosphates, isopentenyl pyrophosphate), in (ii) structural elements of the cell (e.g., DNA, phospholipids, and protein phosphates), in (iii) the energy management of the cell (e.g., ATP, phosphoenol pyruvate (PEP)) and in (iv) messenger molecules (e.g., myoinositol triphosphate, cAMP). Their phosphonate counterparts are found far less widespread in living organisms [20].
Tailoring Triacylglycerol Biosynthetic Pathway in Plants for Biofuel Production
Published in Arindam Kuila, Sustainable Biofuel and Biomass, 2019
Kshitija Sinha, Ranjeet Kaur, Rupam Kumar Bhunia
The movement of organic acids between peroxisome and cytosol affect both glyoxylate cycle and β-oxidation equally but the mechanism of transport is still not known. However, it has been seen that oxaloactetate is incapable of crossing the peroxisomal membrane, and so it is first converted into aspartate by the action of an enzyme called aspartate aminotransferase and then is taken up by the mitochondria in exchange of glutamate and alpha ketoglutarate. These organic acids formed in the glyoxylate pathway further participate in gluconeogenesis. One of the major events of this process is oxaloactetate getting converted into phosphoenolpyruvate (PEP) by PEP carboxykinase. There is a loss of CO2 and ATP is also consumed in this reaction but then glycolytic enzymes convert PEP to sugar phosphates, allowing their participation in the synthesis of sucrose. The sugars formed by this process then participate in growth and development of the seedlings (Graham, 2008).
Biochemistry
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Because of the lack of a Krebs cycle, Cryptosporidium may rely solely on glycolysis as its energy source. It can utilize polysaccharides, including amylopectin, amylose, and hexoses such as glucose and fructose (Figure 3.1). All enzymes catalyzing reactions from hexose to pyruvate are present in the genome, in which hexokinase (HK) consumes one ATP in activating hexose, whereas phosphoglycerate kinase (PGK) and pyruvate kinase (PK) may each produce two ATPs when a single hexose is completely converted into two pyruvate molecules. Unlike humans or other typical aerobic organisms that use an ATP-dependent phosphofructokinase (ATP-PFK), but similar to some other microanaerobic protists including Trichomonas and Giardia, Cryptosporidium uses a pyrophosphate-dependent PFK (PPi-PFK) to economize ATP consumption, for which the activity was previously detected in oocysts (Denton et al., 1996). Because Cryptosporidium does not have a Krebs cycle to completely oxidize carbohydrates, this parasite can generate only 3 net ATP molecules from a single hexose, which is much fewer than those generated by the aerobic pathway (up to 36 ATPs), but significantly higher than typical glycolysis that uses ATP-PFK (only 2 net ATPs). Phosphoenolpyruvate (PEP) may be directly converted to pyruvate by PK, or indirectly via PEP carboxylase (PEPCL), malate dehydrogenase (MDH), and malic enzyme (ME). Although a weak activity of glycerol kinase (GK) catalyzing the formation of glycerol from glycerol-3P was previously reported in oocyst extracts (Entrala and Mascaro, 1997), its gene ortholog cannot be found in either the C. parvum or C. hominis genome, suggesting that glycerol is not one of the end products for generating another ATP as seen in some other protists including trypanosomes (Kralova et al., 2000). However, Cryptosporidium is able to use glycerol-3P to synthesize phospholipid or other complex lipids.
Changes in biochemical composition and fatty acid accumulation of Nannochloropsis oculata in response to different iron concentrations
Published in Biofuels, 2021
Soheila Sabzi, Mehdi Shamsaie Mehrgan, Houman Rajabi Islami, Seyed Pezhman Hosseini Shekarabi
Moreover, an increase in lipid content of Ankistrodesmus falcatus was observed when the media was supplemented with high Fe concentration in combination with nitrogen and phosphorus deficient condition [51]. The mechanism of lipid accumulation in microalgae grown with Fe supplementation can be clarified by many factors. First, elevated phosphoenolpyruvate carboxylase (PEPC) which is active in plants can be influenced by low-Fe condition [52]. PEPC is a firmly controlled enzyme which catalyzes irretrievably, the β-carboxylation of phosphoenolpyruvate (PEP) in the presence of bicarbonate (HCO3−) for the formation of four-carbon to form oxaloacetate and inorganic phosphate. The enzyme is widely dispersed in all plants, green algae, cyanobacteria, and also, archaea and non-photosynthetic bacteria. Furthermore, it is responsive to the fixing of CO2 in photosynthetic fusion of C4 photosynthesis and crassulacean acid metabolism [53]. Moreover, PEPC is a replenishing intermediate in the tricarboxylic acid (TCA) cycle. Hence, it makes available, carbon skeletons for assimilation of biosynthetic pathways and nitrogen [3,53,54]. Down-regulation of PEPC reduced oxaloacetate, a pioneer in amino acid biosynthesis, and increased pyruvate and acetyl-CoA, which are fundamental precursors in lipid and fatty acid biosynthesis [55]. Previous work demonstrated the role of malic enzyme (ME), which is vital for production of NADPH for fatty acid synthesis and desaturation [56–58]. Hence, malate is present in intermediate of the TCA cycle, and influenced by activity of the MEs. Afterwards, it was converted into pyruvate and decreased NADP+, concurrently producing CO2 and NADPH [53,57]. It was considered that the improvement of NADPH as an energy supply, which is due to ME overexpression, was employed by the enzymes involved in TAG synthesis and was induced to elevate lipid production. Increasing access to NADPH increases the reaction rapidity of NADPH that requires enzymes involved in FA synthesis such as acetyl-CoA carboxylase (ACCase) and ATP citrate lyase [53,59]. However, both highest and lowest Fe stress studied in this experiment had strong impact on lipid content of N. oculata, which led to increasing lipid accumulation in the cells. Cells were cultured under laboratory condition with batch culturing technique, showing that Fe-depletion is possibly accountable for the improvement of lipid ratio in N. oculata. The present study illustrates that lipid content of the microalgae grown at 0.63 mg/L FeCl3 concentration was remarkably higher (32.47%) than those cultivated in primary culture medium (20.56% control). Many investigators showed that lipid contents of microalgae species under stressful growth conditions tend to elevate neutral lipids, mostly TAGs, and the biosynthesis of polar lipids into triacylglycerol [4,12]. Conversely, the moderately high Fe cluster in the algae culture medium could be influenced by the significant lipid value, therefore increase in Fe concentration might limit the lipid synthesis pathways [3,17,60].