Dimethyl sulfide, methionine methyl

This enzyme [EC 3.3.1.2], also referred to as -adenosyl-methionine cleaving enzyme and methylmethionine-sulfonium-salt hydrolase, catalyzes the hydrolysis of -adenosylmethionine to produce methylthioadenosine and homoserine. The enzyme will also convert methyl-methionine sulfonium salt to dimethyl sulfide and homoserine. 

Methionine Methyl mercaptan (s) Dimethyl sulfide (m) Dimethyl disulfide (1)... 

Thus, among the sulfur amino acids, hydrogen sulfide is a likely derivative of cysteine, and dimethyl disulfide is a likely derivative of cystine. The formation of dimethyl sulfide and dimethyl disulfide from methionine is readily deduced from expected recombinations of thiomethyl and methyl free radicals. Dimethyl disulfide is the major product. 

Group 3 volatiles, formed by further interactions, can reach even lower threshold values than those mentioned so far, particularly when sulfur is involved, usually derived by the break down of cysteine (bis(2-methyl-3-furyl) disulfide, 0.00002 2-methyl-3-furanthiol, 0.0004 2-furylmethanethiol, 0.005 dimethyl trisulfide, 0.01 dimethyl disulfide, 0.16 dimethyl sulfide, 0.3 hydrogen sulfide, 10). Into some volatile sulfur compounds other atoms as well as the sulfur of cysteine are incorporated (2-acetylthiazoline, 1 5-acetyl-2,3-dihydro-l,4-thiazine, 1.25 2-acetylthiazole, 10). Other volatiles are more likely to be derived from methionine (methanethiol, 0.2). 

Figure 2. Proposedformation of methyl sulfide, dimethyl sulfide and dimethyl disulfide from methionine (adoptedfrom Yoo et al.(31) with permission).

Hattula, T. and Granroth, B., 1974. Formation of dimethyl sulfide from S-methyl-methionine in onion seedlings (Allium cepa). J. Sci. Food Agric., 25 1517—1521. 

Analysis of samples showed that concentrations of methanethiol and dimethyl disulfide were lower in caraway- and TBHQ-treated broccoli florets than in control samples (Table V). Dimethyl tiisulfide was not detected in the refrigerated samples which indicated that its contribution to the objectionable odors of modified atmosphere stored broccoli florets was minimal. Dimethyl sulfide which has a precursor (Sr methyl methionine sulfonium salt 34) different from that for methanethiol-related compounds was present in all samples. 

Diallyl sulfide -Diallyl disulfide -Diallyl trisulfide Dimethyl sulfides Disulfides Glutathione Methionine Methyl sulfides Propenylsulfides Pseudoscordinine... 

Figure 8,59 Formation of dimethyl sulfide from S-methyl methionine.

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). 

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