ISHS Acta Horticulturae 517: XXV International Horticultural Congress, Part 7: Quality of Horticultural Products
ACCUMULATION AND DECOMPOSITION OF S-METHYLMETHIONINE IN CABBAGE |
| Authors: | S. Takigawa, G. Ishii |
| Keywords: | Brassica oleracea, cabbage, enzyme activity, S-Methylmethionine |
| Abstract:
Cabbage contains S-methylmethionine (vitamin U), which is called an anti-ulcer factor. Vitamin U (VU) is enzymatically or nonenzymatically split into homoserine and dimethylsulfide. Volatile dimethylsulfide is one of the quality components in cabbage. We examined the mechanism of dimethylsulfide formation from decomposition of VU in cabbage by methylmethionine sulfonium hydrolase (MMSHase, EC 3.3.1.2). In stored cabbage, VU content increased with time and depended on the varieties. MMSHase enzyme was obtained by adding 1.5 volume of chilled acetone to the cabbage juice. This freeze-dried acetone powder was stored at -20°C until use. However, enzyme preparation with ammonium sulfate was not suitable for the MMSHase assay. VU was decomposed nonenzymatically by heat tretment or hight pH level. VU was also decomposed enzymatically by addition of acetone powder containing MMSHase. Then the pH optimum for the decomposition was between 7.2 and 7.4. Activities of MMSHase were detected in three fractions by gel filtration, and their molecular weights were estimated 5kDa, 10kDa and 22kDa. However, their activity levels were lower than that of acetone powder without fractionation. | |
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