Simplified Chemistry


acetate–CoA ligase

acetate–CoA ligase EC; systematic name: acetate:CoA ligase (AMP-forming); other names: acetyl–CoA synthetase; acyl-activating enzyme; acetate thiokinase; acetyl-activating enzyme. An enzyme that catalyses a reaction between ATP, acetate, and CoA to form AMP, pyrophosphate, and acetyl-CoA. It is an important enzyme in organisms (e.g. Escherichia coli, many fungi, protozoans, algae) that utilize acetate as a carbon source. Distinguish from acetate– CoA ligase (ADP-forming), EC

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acetaminophen or paracetamol 4-acetamidophenol; N-acetyl-paminophenol; N-(4-hydroxyphenyl)acetamide; a drug widely used as an analgesic and antipyretic. It inhibits formation of prostaglandins within, but not outside the brain. It is metabolized within the liver mostly to glucuronide and sulfate conjugates. A small amount is oxidized to a highly reactive intermediate, Nacetylbenzoquinoneimine, that is normally detoxified by conjugation with glutathione. If it is produced in excess of the capacity of the…

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acesulfame 6-methyl-1,2,3-oxathiazin-4(3H)-one 2,2′-dioxide; a sweet-tasting material that, as the potassium salt, has been used in foods and cosmetics.

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Aces abbreviation for N-(2-acetamido)-2-aminoethane sulfonic acid; 2-ethane sulfonic acid; a Good buffer substance, pKa (20°C) = 6.9.

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aceruloplasminemia or acaeruloplasminaemia a rare autosomal recessive disorder in which plasma ceruloplasmin is severely deficient, characterized by neurological abnormalities and systemic hemosiderosis. Any of at least six mutations in a locus at 3q21-q24 can cause the disease.

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ACC synthase

ACC synthase EC; systematic name: S-adenosyl-L-methionine methylthioadenosine lyase; an enzyme present in plant tissues that catalyses the pyridoxal phosphate-dependent conversion of Sadenosylmethionine to 1-aminocyclopropane-1-carboxylic acid (ACC) and 5′-methylthioadenosine. It has been cloned from various fruits – zucchini (courgette), tomato, apple – and has 48–97% sequence identity in different plants. Tomato contains several genes for the enzyme that are differentially regulated and expressed in response to wounding, ripening,…

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accessory pigment

accessory pigment any of the pigments, such as the yellow, red, or purple carotenoids and the red or blue phycobiliproteins in photosynthetic cells. The carotenoids are always present, whereas the phycobiliproteins occur only in algae belonging to the Rhodophyceae, the Cyanophyceae, and the Cryptophyceae. Strictly speaking, chlorophyll b is also an accessory pigment.

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ACC oxidase

ACC oxidase an enzyme present in plant tissues that catalyses the Fe2+– and ascorbate-dependent oxidation of 1-aminocyclopropane-1- carboxylic acid (ACC) to ethylene, CO2, HCN, and H2O. It is a highly unstable monomer (35 kDa) that is inhibited by Co2+. Its activity increases under conditions of stress and at certain developmental stages (e.g. during fruit ripening).

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a.c. calorimetry

a.c. calorimetry a technique in which the thermal response of a sample to an oscillating heat signal is measured in the form of a temperature wave propagating through the sample. The technique allows the measurement of the heat capacity of the sample on both cooling and heating and the monitoring of its isothermal time-dependence. It is useful in the study of phase transitions in solids and in gel…

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absorption spectrum

absorption spectrum a spectrum produced when electromagnetic radiation is absorbed by a sample. The frequencies of the radiation absorbed are those able to excite the atoms or molecules of the sample from their ground states to excited states. The frequency, ν, at which a particular absorption line occurs depends on the energy difference, ΔE, between that of a particular ground state and that of the corresponding excited state….

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