S -Methylmethionine

Fig. 2.4 The S-methylmethionine cycle and its interaction with the activated methyl cycle. The SMM cycle operates within the activated methyl cycle, and in effect short-circuits it. The reactions mediated by MMT and HMT are shown in bold. THF, tetrahydrofolate CH2-THF, 5,10-methylenetetrahydrofolate,...

Fig. 8.1 Proposed synthetic pathways for dimethylsulfoniopropionate from methionine for three algal and plant species. DMSHB 4-dimethylsulfio-2-hydroxy-butyrate, MTHB 4-methylthio-2-hydroxybutyrate, MTOB 4-methylthio-2-oxobutyrate, SMM S-methylmethionine...

Hanks R (1966) Observations on milky water in Chesapeake Bay. Chesapeake Sci 7 175-176 Hanson A, Rivoal J, Paquet L, Gage D (1994) Biosynthesis of 3-dimethylsulfoniopropionate in Wollastonia biflora (L.) DC evidence that S-methylmethionine is an intermediate. Plant Physiol 105 103-110... 

GS158 Ohtsuki, K., M. Kawabata, K. Taguchi, H. Kokura and S. Kawamura. Determination of S-methylmethionine, vitamin U, in various teas. Agr Biol Chem 1984 48(10) 2471-2475. 

Few accounts of the reactions of coordinated ligands have been published. One recent report indicates that the copper complex of S-methylmethionine yields the copper complex of a-amino-y-butyrolactone and dimethyl sulfide upon heating.8 ... 

Kovatcheva [12] has described a method using an automated amino acid analyser for the determination of S-methylmethionine in cabbage, kohlrabi, celery and sweetcorn. The plant sample is first homogenised with 0.1N hy-... 

Figure 8.1. Chromatograms produced on a 100 mm column of an amino acid analyser with 0.3 N sodium citrate solution (pH 7.00) as eluting agent (a) standard solution containing 1 unol/ml of each amino acid (b) 30 g of cabbage extract purified with Dowex 50-X8 in the ammonium form (0.97 mg of S-methylmethionine) and (c) the same sample as for (b) but after treatment at pH 10.0 for 30 minutes at 120 C. MMS S-methylmethionine, fils histidine, lys lysine, orn ornithine, arg arginine. From [12]...

Following adjustment to pH 6.0, the solution is applied to a SP-Sephadex C-25 column in the sodium form. Amino acids are then eluted with 0.2 M citrate phosphate buffer, pH 8.0, and the effluent evaporated to dryness at 50 °C. The residue is dissolved in 0.1 N hydrochloric acid and applied to the amino acid analyser. Amino acids are separated by passing 0.2 M, pH 8 sodium citrate solution down the column. The S-methylmethionine content can then be obtained from the chromatogram, as illustrated in Fig. 8.1. The results obtained agree reasonably well with those obtained by thin-layer chromatography [13]. 

White (22) has shown that DMS is found in numerous marine macroalgae after alkaline treatment (Table II). He also presented data that indicated two pools of DMS precursors in marine algae. He demonstrated that a relatively stable compound released DMS only after alkaline hydrolysis at 100°C for 2 hours, and speculated that this compound may be S-methylmethionine. 

DMS is formed during the biodegradation of organic sulfur compounds and by the biological methylation of sulfide and methanethiol. Precursors of DMS are methionine, S-methylmethionine, dimethylsulfoniopropionate (DMSP), dimethylsulfonioacetate (DMSA), dimethyl sulfoxide (DMSO), methionine sulfoxide and sulfone, trimethylsulfonium salts, S-methylcysteine, homocysteine, dimethyl disulfide (DMDS), 2-keto-4-methiolbutyrate, and 2-mercaptoacetate (thioglycollate). 

Methionine and its S-methyl derivative, S-methylmethionine, are probably important precursors of DMS in terrestrial regions. However, plants also produce a variety of nonprotein sulfur amino adds such as S-methylcysteine, its 7-glutamyl and sulfoxide derivatives, and djenkolic add (44). The biosyntheses and functions of these compounds are poorly understood, and mechanisms for their biodegradation may be of more than academic interest, particularly with respect to the generation of volatile sulfur compounds. 

Methionine 7 -lyase Methionine Homocysteine S-methylcysteine Methionine sulfoxide Methionine sulfone S-methylmethionine (weak) Methanethiol HtS Methanethiol DMS... 

Ko, S., Eliot, A., Kirsch, J. (2004). S-methylmethionine is both a substrate and an activator of 1-aminocyclopropane-l-carboxylate synthase. Arc/t. Biochem. Biophys., 421, 85-90. 

Loscos Deodad, N., Segurel, M., Dagan, L., Sommerer, N., Marlin, T., Baumes, R. (2007). Identification of S-methylmethionine in Petit Manseng grapes as DMS precursor in wine. Anal. Chim. Acta, submitted. 

Rouillon, A., Surdin-Keijan, Y., Thomas, D. (1999). Transport of sulfonium compounds. Characterization of the S adenosylmethionine and S-methylmethionine permeases from the yeast Saccharomyces cerevisiae. J. Biol Chem., 274, 28096-28105. 

Greene, R.C. and Davis, N.B., 1960. Biosynthesis of S-methylmethionine in the jack bean. Biochim. Biophys. Acta, 43 360—362. 

S-methylmethionine-homocysteine methyltransferase, functions along with Sam4p in the conversion of S-adenosylmethionine (AdoMet) to methionine to control the methionine/AdoMet ratio Carbonic anhydrase poorly transcribed under aerobic conditions and at an undetectable level under anaerobic conditions involved in non-classical protein export pathway... 

Methionine in plants can be converted to the sulfonium compound S-methyl-L-methionine, also called vitamin U. It has strong osmoprotectant activity and accumulates in many marine algae and some flowering plants.Other organisms, including mammals, can use S-methylmethionine to methylate homocysteine, converting both reactants back to methionine enabling animals to meet some of their methionine need from this source. 

An enzyme preparation from jack bean meal will transfer a methyl group from S-methylmethionine 167 to homocysteine 148 to yield 2 mol of methionine 149. Use of the doubly labeled compounds 166a and 166b, separated by the method of Cornforth et al. (160), conversion to the (Cs, Sj)- and (Cj, Ss)-isomers of methylmethionine 167a and 167b, and incubation with the enzyme, allowed mass spectrometry to be used to show that the pro-R methyl group of S-methylmethionine is transferred to L-homocysteine 148 (161,162), as shown in Scheme 52. 

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