METHYLATION — chemical reaction, at a cut instead of atom of metal or hydrogen atom is entered into a molecule the hydrocarbon radical marked (— CH 3 ). M.'s processes are eurysynusic in animal organisms; such connections, as creatine (see), adrenaline (see), sincaline (see), methionine (see), thymine etc., are formed by M. of the corresponding predecessors. Disturbance of processes of M. and transmethylation leads to damage of a liver (fatty dystrophy, etc.), kidneys (hemorrhage) and other bodies. M.'s reaction is widely applied in the chemical industry and in a lab. to practice for various sintez, including for receiving metilirovanny derivative sugars and other connections at gas-liquid chromatography (see).
For the first time biol. To m in animal fabrics (transformation of pyridine into methylpyridin) it was shown in 1887 it. researcher W. His. Further fact biol. The m was confirmed with numerous pilot studies. In 1939 an amer. the chemist V. Vinyo entered representation about biol, transmethylation, i.e. about enzymatic transfer of methyl groups from one substances (donators) on other (acceptors). The most important donator of methyl groups is S-adenozilmetioyain, to-ry is formed of methionine with participation of ATP. S-adenozilmetioyain contains high-energy methylsulphonium communication and easily gives methyl group to various acceptors in the presence of the corresponding enzymes.
Most often to substitution by methyl the mobile hydrogen atoms which are at oxygen (— IT) are exposed, to sulfur (— SH) and nitrogen (— NH 2 ). In organic synthesis such vigorous methylating agents as use methyl alcohol (see), dimethyl sulfate (see), methylhalogenides, especially methyl iodide (CH 3 I), methyl bromide (see) and diazomethane (CH 2 N 2 ).
Bibliography Lenindzher A. Biochemistry, the lane with English, M., 1976; H e of a ft-f x S. A. O biological methylation and transmethylation, Usp. sovr, biol., t. 23, century 1, page 1, 1947, bibliogr.; Circassian L. A. Holin as food factor and pathology of choline exchange, M., 1953, bibliogr.; His W. tiber das Stoff-wechsel product der Pyridins, Naunyn-Schmiedeberg’s Arch. exp. Path. Pharmak., Bd 22, S. 253, 1887.
V. I. Rozengart.