Metabolism and Cell Structure

A benzothiazole ring plays an important role in pharmacological target diseases, including metabolic diseases, cancer, anti-inflammatory, neurodegeneration, viral diseases, bacterial infections, fibrosis, and thrombosis. Hydrazone-hydrazide derivatives are present in numerous biological molecules and play a significant role in medicine and pharmacology.

9p viaburame 14-03-2025 1 1   Download

- Polysaccharides are macromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages. - Some polysaccharides serve as storage material, hydrolyzed as needed to provide sugar for cells. - Other polysaccharides serve as building material for structures that protect the cell or the whole organism. - The architecture and function of a polysaccharide are determined by its sugar monomers and by the positions of its glycosidic linkages.

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Chapter 22 "Metabolic Pathways for Carbohydrates" Metabolism and Cell Structure, ATP and Energy, Digestion of Carbohydrates, Glycolysis Oxidation of Glucose, Utilization of Glucose

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DNA of prokaryotes is in a nonequilibrium structural state, characterized as ÔactiveÕ DNA supercoiling. Alterations in this state a€ect many life processes and a homeostatic control of DNA supercoiling has been suggested [Menzel, R. & Gellert, M. (1983) Cell 34, 105±113]. We here report on a new method for quantifying homeostatic control of the high-energy state of in vivo DNA. The method involves making small perturbation in the expression of topoisomerase I, and measuring the e€ect on DNA supercoiling of a reporter plasmid and on the expression of DNA gyrase....

8p system191 01-06-2013 38 5   Download

Trehalose metabolism is an essential component of the stress response in yeast cells. In this work we show that the products of the principal genes involved in trehalose metabolism in Schizosaccharomyces pombe, tps1+ (coding for trehalose6-P synthase, Tps1p), ntp1+ (encoding neutral trehalase, Ntp1p) and tpp1+ (that codes for trehalose-6-P phosphatase, Tpp1p), interact in vitro with each other and with themselves to form protein complexes. Disruption of the gene tps1+ blocks the activation of the neutral trehalase induced by heat shock but not by osmotic stress.

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A severe challenge to the idea that mitochondrial DNA mutations play a major role in the aging process in mammals is that clear loss-of-function mutations accumulate only to very low levels (under 1% of total) in almost any tissue, even by very old age. Their accumulation is punctate: some cells become nearly devoid of wild-type mitochondrial DNA and exhibit no activity for the partly mitochondrially encoded enzyme cytochrome c oxidase. Such cells accumulate in number with aging, suggesting that they survive indefinitely, which is itself paradoxical....

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Antizyme is a polyamine-induced cellular protein that binds to ornithine decarboxylase (ODC), and targets it to rapid ubiquitin-independent degradation by the 26S proteasome. However, the metabolic fate of antizyme is not clear. We have tested the stability of antizyme in mammalian cells. In contrast with previous studies demonstrating stability in vitro in a reticulocyte lysate-based degradation system, in cells antizyme is rapidly degraded and this degradation is inhibited by specific proteasome inhibitors. ...

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The human replication protein Cdc6p is translocated from its chromatin sites to the cytoplasm during the replication phase (S phase) of the cell cycle. However, the amounts of Cdc6p on chromatin remain high during S phase implying either that displaced Cdc6p can rebind to chromatin, or that Cdc6p is synthesized de novo. We have performed metabolic labeling experiments and determined that [35S]methionine is incorporated into Cdc6p at similar rates during the G1 phase and the S phase of the cell cycle. Newly synthesized Cdc6p associates with chromatin....

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Hexadecylphosphocholine (HePC) is a synthetic lipid rep-resentative of a new group of antiproliferative agents, alkylphosphocholines (APC), which are promising candi-dates in anticancer therapy. Thus we have studied the action of HePC on the human hepatoblastoma cell line HepG2, which is frequently used as a model for studies into hepatic lipid metabolism.

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Traditional analyses of the control and regulation of steady-state concentrations and fluxes assume the activities of the enzymes to be constant. In living cells, a hierar-chical control structure connects metabolic pathways to signal-transduction and gene-expression. Consequently, enzyme activities are not generally constant. This would seem to compromise analyses of control and regulation at the metabolic level.

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The elongation phase of mRNA translation is the stage at which the polypeptide is assembled and requires a substantial amount of metabolic energy. Translation elongation in mammals requires a set of nonribosomal proteins called eukaryotic elongation actors or eEFs. Several of these proteins are subject to phosphorylation in mammalian cells, including the factors eEF1A and eEF1B that are involved in recruitment of amino acyl-tRNAs to the ribosome.

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Liver microsomal preparations are routinely used to predict drug interactions that can occurin vivo as a result of inhi-bition of cytochrome P450 (CYP)-mediated metabolism. However, the concentration of free drug (substrate and inhibitor)at its intrahepatic site of action, a variable that cannot be directly measured, may be significantly different from that in microsomal incubation systems.

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Anumber of cellular systems cooperate in redox regulation, providing metabolic responses according to changes in the oxidation (or reduction)of the redox active components of a cell. Key systems of central metabolism, such as the 2-oxo acid dehydrogenase complexes, are important participants in redox regulation, because their function is controlled by the NADH/NAD + ratio and the complex-bound dihydro-lipoate/lipoate ratio.

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Erythrocytic stages of the malaria parasitePlasmodium fal-ciparumrely on glycolysis for their energy supply and it is unclear whether they obtain energy via mitochondrial res-piration albeit enzymes of the tricarboxylic acid (TCA) cycle appear to be expressed in these parasite stages. Isocitrate dehydrogenase (ICDH) is either an integral part of the mitochondrial TCA cycle or is involved in providing NADPH for reductive reactions in the cell.

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The abundance and size of cellular organelles vary depending on the cell type and metabolic needs. Peroxisomes constitute a class of cellular organ-elles renowned for their ability to adapt to cellular and environmental conditions. Together with transcriptional regulators, two groups of per-oxisomal proteins have a pronounced influence on peroxisome size and abundance.

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To assess the expression and physiological role of the mitochondrial NAD + -independent lactate dehydrogenase (iLDH) inEuglena gracilis, cells were grown with different carbon sources, and theD-andL-iLDHactivities and several key metabolic intermediates were examined. iLDH activity was significant throughout the growth period, increasing by three- to fourfold from latency to the stationary phase. Intracellular levels ofD-andL-lactate were high (5–40 mM) fromthe start of the culture and increased (20–80 mM)when the stationaryphasewas entered....

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This work proposes a model of the metabolic branch-point between the methionine and threonine biosynthesis path-ways inArabidopsis thalianawhich involves kinetic compe-tition for phosphohomoserine between the allosteric enzyme threonine synthase and the two-substrate enzyme cysta-thionine c-synthase. Threonine synthase is activated by S-adenosylmethionine and inhibited by AMP. Cystathio-ninec-synthase condenses phosphohomoserine to cysteine via a ping-pong mechanism.

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One of the most drastic post-translational modification of proteins in eu-karyotic cells is poly(ADP-ribosyl)ation, catalysed by a family enzymes termed poly(ADP-ribose) polymerases (PARPs). In the human genome, 18 different genes have been identified that all encode PARP family members.

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Insulin resistance is a cardinal feature of type 2 diabetes and also a conse-quence of trauma such as surgery. Directly after surgery and cell isolation, adipocytes were insulin resistant, but this was reversed after overnight incu-bation in 10% CO2 at 37
C 2 . Tyrosine phosphorylation of the insulin receptor and insulin receptor substrate (IRS)1 was insulin sensitive, but protein kinase B (PKB) and downstream metabolic effects exhibited insulin resistance that was reversed by overnight incubation....

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Transcription of yeast phospholipid biosynthesis structural genes, which contain an inositol-sensitive upstream activa-ting sequence in their promoters, responds to the availability of the soluble precursors inositol and choline and to changes in phospholipid metabolism.

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