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

Abstract

($) S-methyl-L-cysteine sulfoxide (MCS) was scarcely found in seeds of Chinese cabbage, but was present in relatively large amounts in all plant parts after germination. Changes in MCS content paralleled those for soluble sulfur content of tissue. When Na₂³⁵SO₄ was fed to plants, the ³⁵S was predominantly incorporated into MCS in the free amino acid fraction in both sulfur-sufficient and deficient plants, but it was incorporated to a greater extent in the former. ³⁵S-MCS was metabolized more readily in deficient than in sufficient plants, and its sulfur was found not only in various soluble compounds but in the insoluble fractions from plants as well. These results indicate that MCS is a conspicuous constituent in the free amino acid pool of Chinese cabbage and may play an important role in sulfur metabolism by acting as a soluble pool for organic sulfur.