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The Presence of (+)‐S‐Adenosyl‐l‐Methionine in the Rat Brain and Its Lack of Effect on Phenylethanolamine N‐Methyltransferase Activity

Abstract: (+)‐S‐Adenosyl‐l‐methionine [(+)‐SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by 1H‐NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)‐SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse‐phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N‐methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)‐SAM has no effect on phenylethanolamine N‐methyltransferase activity; therefore, it is unlikely that (+)‐SAM plays any possible role in regulation of adrenaline synthesis in the brain.