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Metabolic Cardiology
Published in Stephen T. Sinatra, Mark C. Houston, Nutritional and Integrative Strategies in Cardiovascular Medicine, 2022
The chemical energy held in ATP is resident in the phosphoryl bonds, with the greatest amount of energy residing in the outermost bond holding the ultimate phosphoryl group to the penultimate group. When energy is required to provide the chemical driving force to a cell, this ultimate phosphoryl bond is broken, and chemical energy is released. The cell then converts this chemical energy to mechanical energy to do its work.
The Mannitol Enzyme II of the Bacterial Phosphotransferase System: A Functionally Chimaeric Protein with Receptor, Transport, Kinase, and Regulatory Activities
Published in James F. Kane, Multifunctional Proteins: Catalytic/Structural and Regulatory, 2019
Milton H. Saier, John E. Leonard
Figure 1 shows the pathway for the initiation of D-mannitol catabolism in E. coli. The sugar is transported across the membrane and concomitantly phosphorylated by a PTS-mediated mechanism. In this process the phosphoryl group of phosphoenolpyruvate is transferred sequentially from phosphoenolpyruvate to Enzyme I and HPr, the two energy coupling proteins of the phosphotransferase system. Phospho-HPr then binds to the cytoplasmic surface of the Enzyme II,Mtl and free mannitol, in the extracellular medium, approaches the sugar binding site on the outer face of the enzyme. Group translocation of the sugar through the membrane corresponds to the simultaneous transport and phosphorylation of the substrate, with the release of D-mannitol-1-phosphate in the cytoplasm. The byproduct of this reaction is pyruvate. Cytoplasmic mannitol-1-phosphate is then oxidized to fructose-6-phosphate in a process catalyzed by mannitol-1-phosphate dehydrogenase in which NAD+ serves as the electron acceptor. While the general energy coupling proteins of the PTS, Enzyme I, and HPr, are coded for by the ptsl and ptsH genes, respectively, which comprise the pts operon,9,10 the Enzyme IIMtl and the mannitol-1-phosphate dehydrogenase are coded for by the mtlA and mtlD genes, respectively, which comprise the mtl operon.11,12,13 Substantial differences between the protein constituents of the PTS in the two principal organisms under study, E. coli and S. typhimurium, have not been revealed by available investigations.
Nonhistone Nuclear Phosphoproteins
Published in Lubomir S. Hnilica, Chromosomal Nonhistone Proteins, 2018
In spite of the progress made, there is still no unified picture encompassing nonhistone phosphoprotein function. In fact, the nuclear phosphoproteins are a diverse group of proteins which cover a broad range of functions. Although the evidence for involvement with transcription as proposed in the mid-1960s has been strengthened, additional roles have become apparent. In particular, phosphoproteins seem to be participants in the controlled assembly of various nuclear substructures such as nuclear membranes, nuclear and nucleolar RNP particles, and nucleosomes. In addition, several nuclear enzymes are phosphorylated: RNA polymerases, poly(A) polymerase, and histone deacetylase. Thus, the phosphoryl group is called upon to perform a multitude of tasks, some of them related to one another and others unrelated.
Design, synthesis and characterization of enzyme-analogue-built polymer catalysts as artificial hydrolases
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Divya Mathew, Benny Thomas, Karakkattu Subrahmanian Devaky
The first artificial esterase with the imprints of TSA was reported by the same group of Mosbach [47]. In 1989, D.K. Robinson and K. Mosbach detailed molecular imprinting of p-nitrophenyl methylphosphonate, a transition state analogue of hydrolytic reactions, through Co(II) ion mediated polymerization utilizing poly [4(5)-vinylimidazole] as the functional monomer and 1,4-dibromobutane, as the bifunctional crosslinker. This polymer catalyst was an efficient esterase for p-nitrophenyl acetate (Figure 10). The print TSA molecule, p-nitrophenyl methylphosphonate indicated structural resemblance with the substrate molecule p-nitrophenyl acetate, but contains a tetrahedral phosphoryl group in place of the carboxyl group. The artificial esterase MIP exhibited 60-fold catalytic competence over the control polymer CP. Further, they announced the print TSA molecules as a competitive inhibitor for p-nitrophenyl acetate.
Sirt1 modulates H3 phosphorylation and facilitates osteosarcoma cell autophagy
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Hongliang Ying, Boda Ying, Jinrui Zhang, Daliang Kong
Sirt1 is a member of the sirtuin family comprised of seven members, Sirt1 to Sirt 7 [26]. As well-studied histone deacetylation and methylation enzyme, Sirt1 has been discovered to be highly expressed in a number of tumor cells, including osteosarcoma cells [16,26]. It is reported that overexpression of Sirt1 is associated with the activated oncogenes and silenced tumor suppressor genes in osteosarcoma cells [27,28]. H3 is a key component of nucleosome [29]. Phosphorylation of H3 has been discovered to engage in the regulation of chromosome condensation and transcriptional modulation [30]. Herein, we found that osteosarcoma cells with high expression of Sirt1 generally had high expression of H3T3ph. Overexpression of Sirt1 elevated the H3T3ph level in osteosarcoma cells, while the silence of Sirt1 lowered the H3T3ph level. The results of co-immunoprecipitation assay and GST pull-down assay indicated that Sirt1 could directly interact with H3 and phosphorylate H3T3. These outcomes illustrated that except for histone deacetylase and methylase activity, Sirt1 also could exhibit histone phosphoryl transferase activity.
Interaction of low frequency external electric fields and pancreatic β-cell: a mathematical modeling approach to identify the influence of excitation parameters
Published in International Journal of Radiation Biology, 2018
Sajjad Farashi, Pezhman Sasanpour, Hashem Rafii-Tabar
The glycolysis pathway contains a series of reactions for converting glucose into pyruvate and ATP. In the first step glucose is phosphorylated and converted to glucose-6-phosphate (G6P) which will be isomerised to the fructose-6-phosphate (F6P). The further phosphorylation of F6P by phosphofructokinase-1 enzyme produces fructose 1,6-bisphosphate, which in the next step will be cleaved into glyceraldehyde-3-phosphate (G3P) and dihydroxy acetone phosphate (DHAP) using aldolase enzyme. The DHAP is converted to further G3P by triose-phosphate isomerase. This phase, the procedure is preparatory phase and requires energy consumption. In the next step G3P oxidized to 1,3-bisphosphoglycerate incorporating glyceraldehyde 3-phosphate dehydrogenase. A large amount of energy during the oxidation of an aldehyde group will be released. In this step Nicotinamide adenine dinucleotide (NAD+) will be reduced to NADH, the reduced form of NAD+. The enzyme phosphoglycerate kinase transfers the phosphoryl group of 1,3-bisphosphoglycerate to ADP and producing ATP and 3-phosphoglycerate which the latter will be isomerized to 2-phosphoglycerate using Phosphoglycerate mutase. Using the enzyme enolase, 2-phosphoglycerate will be converted to phosphoenolpyruvate (PEP). Finally, PEP will be converted to pyruvate by pyruvate kinase. In this step one extra ATP molecule will be produced. The glycolysis pathway is depicted in Figure 1.