Metabolite analogues definition, derivation, and mode of action

1 Metabolite analogues definition, derivation, and mode of action 

Those metabolites (substrates or coenzymes) that are present in only small amounts in a cell or tissue can be antagonized by substances known as metabolite analogues. The molecules of each such analogue have a region which is similar to that region of the metabolite which makes contact with 

Several examples of competition between simple anions have been observed. Thus the perchlorate and the thiocyanate anion inhibit concentration of the iodide anion by the thyroid gland, without affecting the oxidative incorporation of the iodide anion into thyroxine (Stanbury and Wyngaarden, 1952). Likewise, the organism Nitrobacter which oxidizes nitrite to nitrate, is inhibited by cyanate or chlorate (anions), an effect easily reversed by washing (Lees and Simpson, 1957). 

Small molecules are sometimes antagonized by their near homologues, e.g. malonic acid (9.1) antagonizes the oxidation of succinic acid (9.2) by succinic dehydrogenase (Quastel and Wooldridge, 1927). 

Sometimes antagonists have been made by substituting fluorine for hydrogen, e.g. p-fiuorophenylalanine as an antagonist for phenylalanine. 

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Enzymes, their substrates and other metabolites. 289 Metabolite analogues definition, derivation, and mode of action. 295 History of metabolite antagonism prior to 1940. 302 The folic acid antagonists. 303... 

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