S-Adenosyl-l-Methionine in the Synthesis of Choline, Creatine, and Cysteine in Vivo and in Vitro

Abstract

Cantoni (1) has demonstrated that the requirement for adenosine triphosphate in the synthesis in vitro of creatine and N'methylnicotinamide from methionine and guanidoacetic acid and nicotinamide, respectively, is due to the formation of S-adenosylmethionine from methionine and ATP,' the compound being the direct donor of its methyl group to the respective acceptors.As far as we are aware, no information is available as to whether or not S-adenosylmethionine is also the direct donor of its methyl group in the biosynthesis of choline, or whether or not its homocysteine moiety is available for the biosynthesis of cysteine.Such a study is reported in the present communication along with a convenient method of preparation of S-adenosyl-n-methionine bromide, labeled with Cl4 in the methyl group, carbon 2 of the homocysteine moiety, or labeled with S35.EXPERIMENTAL Preparation of X-Adenosylmethionine-The respectively labeled S-adenosylmethionine was obtained in essentially the same yields employing L-methionine-CH3-CY4, nn-methionine-2-C14, or methionine-S35.Commercial baker's yeast that was grown, harvested, and extracted according to Schlenk and De Palma (2), was used.The method of isolation of S-adenosylmethionine, however, was modified in order to eliminate the need for exchange columns and large volumes of eluates.From yeast perchloric acid extracts, the salt of S-adenosylmethionine was isolated according to the method described for the isolation of methionine methyl sulfonium bromide (3).The yields of S-adenosylmethionine bromide varied from 6 to 9 per cent of the substrate methionine (in mmoles) .A 3 liter round-bottom flask was fitted with a 2-holed rubber stopper with sintered glass aerator and a vacuum line lead.Air was drawn into the culture vessel after passage through a gasbubbling train consisting of a 6 N HzSOl scrubber and two water scrubbers.The medium was made up as follows:1 MgC12.6HzO 1 0.429 gm.CaCL 0.143 gm. 2 / MnSOd.HtO 0.087 gm. 1 ZnS01.7Hs00.143 gm. 3 Sodium citrate 1.428 gm.i i KHzPOd 2.857 gm.(NH&SO,, 2.857 gm. 4 KsHP04 1.428 gm.Glucose, 21.42 gm.; methionine, 6.7 mmoles.