China 
Africa 
Explore chapters and articles related to this topic
Cell Physiology
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Four reactions in glycolysis play key roles in regulating its flux: hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), and 6-phosphofructo 2-kinase/fructose 2,6-bisphosphate (PFKFB) (Panel 3.12). These four enzymes along with pyruvate dehydrogenase kinase (PDK) regulate the flux of glucose carbon and its distribution at the pyruvate node. We will take a simplified view to largely divide glycolysis into two types of metabolism: one high flux in proliferating cells and the other low flux in quiescent cells (Figure 3.9). These two types of metabolism are influenced by the isoforms involved, the composition of the medium, and the growth rate, among other factors. With some isoform combinations, a number of reaction steps are activated by the accumulation of F2,6P and F1,6P (Figure 3.9a). Upon full activation, one may see a 5-fold or higher increase in glucose consumption, whereas with the isoform combination depicted in Figure 3.9b, the degree of activation is much lower. Below, we will describe the allosteric regulation of a few major enzymes that play key roles in determining the flux. Table 3.1 lists the compositions of the isozymes of glycolysis in a few human tissues.
The Pentose Phosphates Pathway—Glucogenesis
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
The most part of the Gibbs energy decline comes from the following three reactional steps which are quasi-irreversible: glucose + ATP→hexokinaseglucose-6-phosphate + ADPfructose-6-phosphate + ATP→phosphofructokinasefructose-1,6-diphosphate + ADPphosphoenolpyruvate + ADP→pyruvatekinasepyruvate + ATP
In Vivo
Published in Nguyễn T. K. Thanh, Clinical Applications of Magnetic Nanoparticles, 2018
Antonella Antonelli, Mauro Magnani
The number of circulating RBCs must be adequate to supply oxygen to tissues. In the case of hypoxia, the haemopoietic stem cells in the bone marrow, stimulated by erythropoietin, go through various phases of development until the mature RBCs can be released into the bloodstream. The mature RBCs are released from the bone marrow into the blood at the reticulocyte stage and reticulocytes become fully functional RBCs after 1–2 days. This process of developing from erythropoietic bone marrow cells to mature RBCs takes only a few days.2 The final stage of maturation, when the cell lacks a nucleus, mitochondria and endoplasmic reticulum requires iron, vitamin B12 and folic acid. The enzymes within the RBC allow it to produce small amounts of energy. Glucose, which is the main energy source for these cells, is metabolized in the glycolytic pathway anaerobically to pyruvate or lactate, producing two molecules of adenosine triphosphate (ATP) per molecule of glucose that is used. Thus, glycolysis is the main energy pathway, and it is regulated in the hexokinase (Hk) and phosphofructokinase steps.3 The most important and functional component of RBCs is haemoglobin, which accounts for the oxygen carrying capacity of these cells. In addition to carrying oxygen, which is the main function of RBCs, they carry out the following functions: (1) conversion of carbon dioxide in bicarbonate, thanks to the enzyme carbonic anhydrase, and its transport to the lungs where it is expelled; and (2) control of pH in the bloodstream by acting as an acid-base buffer.
Microplastics and nanoplastics in the soil-plant nexus: Sources, uptake, and toxicity
Published in Critical Reviews in Environmental Science and Technology, 2023
Nisha Singh, Meshal M. Abdullah, Xingmao Ma, Virender K. Sharma
MPs/NPs interfere with carbohydrates and amino acids and alter the energy supply. Modulation of key enzymes associated with glycolysis metabolism (aldolase, hexokinase, phosphofructokinase) by PS NPs (100 nm) has been reported in wheat (S. Li, Guo et al., 2021). In another study, MPs exposure to wheat also led to the upregulation of galactose metabolism to meet high energy (ATP) demand (Lian et al., 2020). The increase in galactose content reflects the tolerance of plants to NPs. A significant effect of MPs on the activity of carbohydrate metabolizing enzymes was reported in barley (S. Li et al., 2021). Further, authors have reported downregulation of enzyme activity involved in the rate-limiting step in pentose phosphate pathway. The tricarboxylic acid (TCA) cycle, which is one of the major sources of energy production was upregulated in corn (Figure 4j) (Y. Zhang et al., 2022).
Statistical solution and Liouville-type theorem for the nonautonomous discrete Selkov model
Published in Dynamical Systems, 2023
Congcong Li, Chunqiu Li, Jintao Wang
In this article, we consider the following nonautonomous discrete Selkov model: associated with initial conditions where d, a, k are positive constants, and A is a linear operator defined as Equations (1) and (2) can be regarded as a discrete analogue to the following nonautonomous continuous Selkov model on : which was proposed as a simplified model of the phosphofructokinase reactions in glycolysis involving ATP, ADP and AMP, see [26,34] for details. In Equations (4) and (5), d is the diffusion coefficient, and the nonlinear reaction term denotes the type of cubic autocatalytic chemical reactions. On the dynamical behaviour of this Selkov model, You [34] proved the existence of global attractor and established the finiteness of the Hausdorff dimension and fractal dimension of the global attractor. Later, You [35] further verified the upper semicontinuity of the global attractor of reversible Selkov equations. Recently, Jia et al. [18] studied the asymptotic behaviour of the discrete Selkov model (1)–(2) and proved the existence of uniform attractor and established the upper semicontinuity of the uniform attractor for (1)–(2). However, as far as we know, there are few works on statistical solutions of the discrete Selkov model (1)–(2).
Transcriptome analysis reveals that yeast extract inhibits synthesis of prodigiosin by Serratia marcescens SDSPY-136
Published in Preparative Biochemistry & Biotechnology, 2023
Junqing Wang, Tingting Zhang, Yang Liu, Shanshan Wang, Zerun Li, Ping Sun, Hui Xu
The majority of the enriched DEGs involved in the TCA cycle (ko00020), propanoate metabolism (ko00640), inositol phosphate metabolism (ko00562), pyruvate metabolism (ko00620), and butanoate metabolism (ko00650). TCA showed the greatest enrichment, and the majority of the genes associated in pyruvate metabolism were enriched (Table S1). Pyruvate and malonyl-CoA in the carbon metabolism pathway are important intermediates in prodigiosin synthesis.[13] Two key enzymes in the glycolysis pathway were downregulated: 6-phosphofructokinase (EC:2.7.1.11) and glyceraldehyde 3-phosphate dehydrogenase (phosphorylation) (EC:1.2.1.12). Changes in these enzymes affect pyruvate production. In the TCA cycle, we observed downregulation of pyruvate ferredoxin oxidoreductase (porA, B, C, D, G), which provides thiamin pyrophosphate and catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA and CO2.[35] Notably, pyruvate dehydrogenase (aceE), pyruvate dehydrogenase E1 (PDHA, B), and dihydrolipoamide dehydrogenase (DLD) were slightly upregulated (Figure 5). These genes are critical for maintaining normal TCA cycle turnover and increasing pyruvate-to-acetyl-CoA flow.[36] Other genes in the citric acid cycle, such as isocitrate dehydrogenase (icd), 2-ketoglutarate dehydrogenase (OGDH; kgd; DLST), succinyl-CoA synthase (sucCD; LSC1, 2), fumarate hydration enzymes (fumA, B, C, D, E), malate dehydrogenase (mqo), and malate dehydrogenase (MDH1, 2) were also upregulated. The products of these genes are involved in providing energy and carbon skeletons for metabolism in S. marcescens. The expression of phosphoenol pyruvate carboxykinase, which is involved in carbon fixation via pyruvate metabolism, showed an increasing trend at the gene level. The conversion of malonyl-CoA to acetyl-CoA was enhanced, whereas the derivatization of pyruvate to formic and acetic acids was weakened. The regulation of other pyruvate genes is shown in Figure 5. The upregulation of these carbon metabolism genes suggests that S. marcescens carbon metabolism is regulated to compensate for the energy deficit. This may indirectly affect prodigiosin biosynthesis.