Sulfur dioxide glutathione

A possible function of this intracellular sulfur cycle is to buffer, i.e. to homeostatically regulate, the cysteine concentration of the cells. Irrespective of whether sulfate, cysteine, or sulfur dioxide is available as sulfur source, the intracellular sulfur cycle would allow a plant cell to use as much of these compounds as necessary for growth and development. At the same time, it would give a plant cell the possibility to maintain the cysteine pool at an appropriate concentration by emitting excess sulfur into the atmosphere. Thus, emission of hydrogen sulfide may take place when the influx of sulfur in the form of sulfate, cysteine, or sulfur dioxide exceeds the conversion of these sulfur sources into protein, glutathione, methionine, and other sulfur-containing components of the cell. 

Langley-Evans, S.C., G.J.Phillips, and A.A.Jackson. 1996. Sulfur dioxide A potent glutathione depleting agent. Comp. Biochem. Physiol. C Pharmacol. Toxicol. Endocrinol. 114(2) 89—... 

In addition to the sulfur-containing amino acids methionine and cysteine, inorganic sulfate, sulfur dioxide and organic sulfur compounds such glutathione, taurine and N-acetyl-methionine (to a lesser extent) are also important for the sulfur intake by sparing the required amounts of methionine and cysteine in the diet. The natural content of sulfur dioxide of food is far lower than the total sulfur content (Table 5.4). Sulfur dioxide is used for food conservation, and this in turn has led to the proposal of upper limit values for this sulfur compound (see Section 5.7 and Table 5.11). 

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