抄録
Free L-cysteine was detected in the cell sap of the green alga Valonia macrophysa using high perfor-mance gel filtration chromatography and fluorometric detection after pre-column derivatization with the thiol-specific reagent N-(7-dimethylamino-4-methylcoumarinyl) maleimide. Large quantities of cysteine (up to 39.3μg/ml) were detected together with small amounts of glutathione when cell sap was prepared without exposure to air at pH 2.0. On the other hand, when sap was exposed to air at pH 7.0 for 2h, cystine rather than cysteine was detected at levelsof 41.7μg/ml using post-column derivatization with ninhydrin reagent. Since the molar ratio of cysteine to cystine was 1.8:1.0, it is probable thatcystine was derived by oxidation of cysteine that must accumulate in cell sap in situ. When the levels of half-cystine were measured for other cell compartments it was found that high molecular weight compounds in cell sap contained high amounts of half-cystine (18.0% of total amino acid pool) compared to the water insoluble fraction of protoplasm-layer and cell wall fractions which contained 8.9% and 7.6% half-cystine, respectively.
