Antimetabolites - substances with similar chemical structure to metabolites, i.e. the compounds, which plays a significant role in metabolism (for example, vitamins, enzymes , etc.,), and is able to enroll in the body to take their place and change the course of metabolic processes. In connection with some differences structure antimetabolites can not provide the normal flow of biochemical reactions, which can lead to severe disorders of vital activity of an organism. Some antimetabolites, selectively violate the metabolism of microorganisms that are used as drugs for treatment of diseases caused by these microorganisms (sulfa drugs, paraaminosalicilovaya acid - PAS and others). Known antimetabolites, slows growth of tumor tissue. If such antimetabolites not cause General disorders of metabolism in the patient, they are used in medicinal anticancer drugs (e.g., mercaptopurine, fluorouracil). See also the Metabolism and energy.

Antimetabolites - substances with similar chemical structure to biologically active compounds and inhibit their action. Having known by the similarity of the configuration and size of a molecule by molecule natural metabolite, an antimetabolite able to take his place, to oust him at certain stages of biochemical reactions. But due to some differences in the structure of the molecule antimetabolites can not provide the normal flow of these reactions, and may cause changes of metabolic processes.
The most important group of antimetabolites are structural analogues of vitamins, hormones and neurotransmitters.
As the majority of vitamins is components of enzymes, the introduction of antimetabolite vitamin (antivitamin) in the body leads to the formation of inactive similar enzyme, is not capable to carry out the inherent normal enzyme functions specific catalyst. As a result of the phenomena characteristic of the deficit of the corresponding vitamin.
For example, when introduced into the body fornicating acid, serving A. vitamin PP - nicotinamide, instead of diphosphopyridine (nikotinamidadenindinkleotid, codeveronica), which is kofermentom dehydrogenases, formed similar nucleotide, in which the place of nicotinamide is amide fornicating acid.
This nucleotide competes for apparment with natural nucleotides, taking his place, but he can't act as a coenzyme in the dehydrogenation reactions. This is the principle of the most antivitamins. Sulfanilamida - analogues of para-aminobenzoic acid; the latter is an integral part of coenzymes group of folic acid.
The therapeutic effect of sulfonamides due to the fact that they are included in the coenzymes microorganisms and thus cause them to violation of vital reactions of metabolism.
One of antimetabolites hormones is a structural analogue of the adrenal cortex hormone cortisone - 2-methyl-9 (a)-forkortet. This connection prevents the development of atrophy of the thymus and follicles spleen, and also some other pathological phenomena caused by steroids.
Powerful antagonist of serotonin, which has a wide range of effects on the body, serve madman, derivatives of lysergic acid diethylamide etc. because some of these antimetabolites cause mental disorders characteristic of schizophrenia (hallucinations, delusions, misconduct and others)believe that metabolic serotonin play a significant role in the pathogenesis of this disease.
A special group A. are analogues of purine and pyrimidine bases, included in the composition of nucleic acids, and analogs of amino acids that build proteins. The thiouracil, a structural analog of uracil, a member of the molecule ribonucleic acid tobacco mosaic virus,tobacco sheet is included in the molecules of nucleic acids newly formed viral particles, then these atypical viruses lose the ability to further reproduction. Similarly, there 6-azauracil on microbial cells, preventing the activation of the natural metabolite of uracil in their nucleic acids. 6-Azauracil has also properties.
Antimetabolites can be used as a chemotherapeutic drugs. In some cases, when during the process of metabolism is abnormal introduction A. can contribute to the normalization of body functions. However, the application of antimetabolites as medicinal substances severely limited by the fact that many of them are antagonists of metabolites as microbial cells and cells of the human body. In such cases, the use A. you may, if the microorganism or diseased tissue has the ability to selectively absorb and accumulate antimetabolites. For example, you can use the analogs of purine and pyrimidine bases as cancerolyticity substances, as the tumor tissue is an intense metabolism, in particular - intensive synthesis of nucleic acids, therefore introduced A. mainly comes in tumor tissue. A. widely used as insecticides, fungicides, disinfectants; for example, hexachloran represents the analogue of Inositol, which is the vitamin for many plant and animal organisms.
Cm. also the Metabolism and anergy.