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Regional Distribution of Methionine Adenosyltransferase in Rat Brain as Measured by a Rapid Radiochemical Method
Author(s) -
Hiemke Christoph,
Ghraf Rüdiger
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb12531.x
Subject(s) - transmethylation , methionine adenosyltransferase , methionine , chemistry , methylation , methyltransferase , specific activity , chromatography , biochemistry , enzyme , amino acid , gene
The distribution of methionine adenosyltransferase (MAT) in the CNS of the rat was studied by use of a rapid, sensitive and specific radiochemical method. The S ‐adenosyl‐[methyl‐ 14 C] l ‐methionine ([ 14 C]SAM) generated by adenosyl transfer from ATP to [methyl‐ 14 C] l ‐methionine is quantitated by use of a SAM‐consuming transmethylation reaction. Catechol O ‐methyltransferase (COMT), prepared from rat liver, transfers the methyl‐ 14 C group of SAM to 3,4‐dihydroxybenzoic acid. The 14 C‐labelled methylation products, vanillic acid and isovanillic acid, are separated from unreacted methionine by solvent extraction and quantitated by liquid scintillation counting. Compared to other methods of MAT determination, which include separation of generated SAM from methionine by ion‐exchange chromatography, the assay described exhibited the same high degree of specificity and sensitivity but proved to be less time consuming. MAT activity was found to be uniformly distributed between various brain regions and the pituitary gland of adult male rats. In the pineal gland the enzyme activity is about tenfold higher.