metabolite

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metabolite,

organic compound that is a starting material in, an intermediate in, or an end product of metabolismmetabolism,
sum of all biochemical processes involved in life. Two subcategories of metabolism are anabolism, the building up of complex organic molecules from simpler precursors, and catabolism, the breakdown of complex substances into simpler molecules, often accompanied by
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. Starting materials are substances, usually small and of simple structure, absorbed by the organism as food. These include the vitamins and essential amino acids. They can be used to construct more complex molecules, or they can be broken down into simpler ones. Intermediary metabolites are by far the most common; they may be synthesized from other metabolites, perhaps used to make more complex substances, or broken down into simpler compounds, often with the release of chemical energy. For example, glucose, perhaps the single most important metabolite, can be synthesized in a process called gluconeogenesis, can be polymerized to form starch or glycogen, and can be broken down during glycolysis in order to obtain chemical energy. End products of metabolism are the final result of the breakdown of other metabolites and are excreted from the organism without further change; they usually cannot be used to synthesize other metabolites. Urea, for example, is an end product of protein degradation in man, the other primates, and the Dalmatian dog. Carbon dioxide is usually thought of as an end product of carbohydrate, protein, and fat degradation in aerobic organisms, although technically, carbon dioxide, as carbonic acid, can participate in the biosynthesis of some substances, particularly in plants. Complex substances such as proteins, although end products of a synthetic process, can almost always be broken down again and are usually not considered to be true end products of metabolism. A compound that closely resembles a metabolite in molecular structure but is metabolically inactive is called an antimetabolite; such a substance is often used as a drug in the treatment of malignant disease. When introduced into the body, it is mistaken by the cell for the metabolite it simulates, thus preventing the cell from using the genuine substance necessary to its life and growth. It is difficult to design molecules so that they will be metabolic poisons for malignant cells and not for normal cells as well. Folic acid (see coenzymecoenzyme
, 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
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) antagonists such as aminopterin and methotrexate are used in the treatment of leukemiasleukemia
, cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets.
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 and other neoplastic diseases. The purine antagonist mercaptopurine is also used for the treatment of acute leukemia, while azathioprine (Imuran) is used to prevent the rejection of transplanted organs. Pyrimidine antagonists used in cancer chemotherapy include fluorouracil and fluorodeoxyuridine. Most of the agents are designed to halt cell division in rapidly dividing malignant cells by the disruption of the metabolism of purines and pyrimidines, two classes of compounds necessary for nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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 synthesis and hence necessary for cell division.

metabolite

[mə′tab·ə‚līt]
(biochemistry)
A product of intermediary metabolism.
References in periodicals archive ?
Since the breakdown product for lindane was not found, this could represent recent exposure.
Chief among these are DDE (dichlorodiphenyldichloroethylene), a breakdown product of the once widely used herbicide DDT (dichlorodiphenyltrichloroethane), and polychlorinated biphenyls (PCBs), once used as dielectric fluids in capacitors and transformers.
The microbes could completely break down the varieties with few branches very quickly; however, other more complex naphthenic acids did not break down completely, with the breakdown products still present," said Johnson.
According to nutrition experts, glucosinolates are not active in the body, but their breakdown products help detoxify carcinogens (cancer-causing toxins) and suppress the growth of existing cancerous tumours.
The breakdown products of protein and fat are important to product flavor.
Calpain activation was induced by addition of a calcium channel opener (maitotoxin) to cells grown to 80% confluence; 145- and 150-kD calpain-specific breakdown products of aII-spectrin (SBDPs) were monitored over time by quantitative Western Blot analysis.
mistakenly state that "it seems to have escaped notice" that breakdown products of OP pesticides occur in the environment, including food.
Such breakdown products include nitriles, isothiocyanates, thiocyanates, epithionitriles and vinyl oxazolidinethiones.
Previous investigations have indicated that CHPDs are not readily absorbed, but their breakdown products are.
The protective pigment, called sporopollenin, and several of its long-lived breakdown products absorb a specific wave-length of ultraviolet radiation, says Lomax.
As reported recently in the journal Carcinogenesis, this new study links the protective effects of fish oils to breakdown products from omega-3 fatty acid metabolism.
The compound, nornicotine, is naturally present in tobacco and is also a metabolite of nicotine, forming about 10% of nicotine breakdown products in the body.