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Definition: coenzyme from The Penguin Dictionary of Science

A non-protein organic molecule that plays an accessory yet necessary role in the catalytic action of an ➤enzyme. Many ➤vitamins function as coenzymes, particularly those of the B group. ➤➤FAD; NAD+; NADP+; thiamine.


coenzyme

From The Columbia Encyclopedia
(kō-ĕn'zīm), any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes . A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in the chemical reactions catalyzed by the enzyme. Often a coenzyme is structurally altered in the course of these reactions, but it is always restored to its original form in subsequent reactions catalyzed by other enzyme systems. Adenosine triphosphate (ATP) is a coenzyme of vast importance in the transfer of chemical energy derived from biochemical oxidations. Other nucleotides (formed from uracil , cytosine , guanine , and inosine) have also been found to act as coenzymes. For example, uridine triphosphate—a derivative of uracil—has been demonstrated to be of great importance in the metabolism of carbohydrates, as in the biosynthesis of glycogen and sucrose. Those coenzymes that have been found to be necessary…
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Full text Article NAD (coenzyme I; cozymase)

From Dictionary of Microbiology & Molecular Biology
NAD (nicotinamide adenine dinucleotide). NADP =...
Nicotinamide adenine dinucleotide (formerly known as diphosphopyridine nucleotide, DPN). NAD is an important coenzyme, functioning as a hydrogen carrier in a wide range of redox reactions; the H is carried on the nicotinamide residue (see figure). The oxidized form of the coenzyme is written NAD + , …
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Full text Article coenzyme

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Small organic nonprotein compound that attaches to an enzyme and is necessary for its correct functioning. Tightly bound coenzymes are known as prosthetic groups; more loosely bound ones are called cofactors. The coenzyme itself is not usually changed during a reaction. If it is, it is usually…
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Full text Article coenzyme

From The Columbia Encyclopedia
(kō-ĕn'zīm), any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes . A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in the chemical…
| 1,125 words
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Full text Article coenzyme

From Library of Health and Living: The Encyclopedia of Nutrition and Good Health
An organic compound required by an enzyme in order for it to function as a catalyst. Coenzymes are low molecular weight, often heat-stable substances, while enzymes are hundreds of times larger and are usually heat sensitive. As enzyme activators, coenzymes combine with the inactive protein ( …
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Full text Article coenzyme Q10

From Library of Health and Living: The Encyclopedia of Nutrition and Good Health
Also known as: coenzyme Q; ubiquinone; vitamin Q 10 A lipid oxidation -reduction agent found in mitochondria , the powerhouses of the cell. Coenzyme Q helps mitochondria oxidize fuels like fat and carbohydrate to produce cellular energy (ATP) in a process known as oxidative phosphorylation . Because…
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Full text Article coenzyme Q10

From Library of Health and Living: The Encyclopedia of Men's Health
A component of the mitochondria of all cells. It carries electrons as part of the production of energy, in the form of ATP. Coenzyme Q10 is synthesized (produced) in the cells, although there is some evidence that in certain diseases, the body cannot produce enough and systemic levels are low. …
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Full text Article coenzyme

From Penguin Dictionary of Biology
Organic molecule (often a derivative of a mononucleotide or dinucleotide) serving as COFACTOR in an enzyme reaction, but, unlike a PROSTHETIC GROUP , binding only temporarily to the enzyme molecule. Often a recycled vehicle for a chemical group needed in or produced by the enzymic process, reverting…
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Full text Article coenzyme

From Britannica Concise Encyclopedia
Any of a number of freely diffusing organic compounds that function as cofactor s with enzyme s in promoting a variety of metabolic reactions. Coenzymes participate in enzyme-mediated catalysis in stoichiometric ( mole -for-mole) amounts, are modified during the reaction, and may require another…
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Full text Article coenzyme A

From Library of Health and Living: The Encyclopedia of Nutrition and Good Health
An enzyme helper based on the B vitamin pantothenic acid that prepares fatty acids and acetic acid to participate in biosynthetic and degradative reactions of cells. For example, when fatty acids are oxidized as fuel, they are first attached to coenzyme A. The enzymatic breakdown of amino acids, …
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See Fig. 122 . Dinucleotide COENZYME , derivative of NICOTINIC ACID , required in small amounts in many REDOX REACTIONS where oxidoreductase enzymes transfer hydrogen (i.e. carry electrons), as in KREBS CYCLE and ELECTRON TRANSPORT SYSTEM (ETS) in respiration. NAD + usually functions in oxidations. …
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