Fate of ($ ) S-methyl-L-cysteine sulfoxide in Chinese cabbage, Brassica pekinensis RUPR.

($) S-methyl-L-cysteine sulfoxide (MCS) was scarcely found inseeds of Chinese cabbage, but was present in relatively largeamounts in all plant parts after germination. Changes in MCScontent paralleled those for soluble sulfur content of tissue. When Na₂³⁵SO₄ was fed to plants, the ³⁵S was predominantly incorporatedinto MCS in the free amino acid fraction in both sulfur-sufficientand deficient plants, but it was incorporated to a greater extentin the former. ³⁵S-MCS was metabolized more readily in deficientthan in sufficient plants, and its sulfur was found not onlyin various soluble compounds but in the insoluble fractionsfrom plants as well. These results indicate that MCS is a conspicuousconstituent in the free amino acid pool of Chinese cabbage andmay play an important role in sulfur metabolism by acting asa soluble pool for organic sulfur. (Received June 22, 1970; )