The formation of sulphur-containing amino acids in germinating seeds of rape (Brassica napus L.) |
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Authors: | T T Ngo and P D Shargool |
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Institution: | Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada |
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Abstract: | Sodium (35)S]sulphide was fed to batches of germinating rapeseed, in some instances with the addition of unlabelled cysteine. Both the total radioactivity and specific radioactivity of the free sulphur-containing amino acids were examined. Cysteine and homocysteine were rapidly labelled; label subsequently appeared in cystathionine and methionine. The results obtained indicated that both the sulphydration and trans-sulphuration pathways were operating. This conclusion was reinforced by the results of experiments in which batches of rapeseed were incubated with l-(14)C]homoserine. These showed the formation of labelled homocysteine, cystathione and methionine. It was thought the trans-sulphuration pathway was making the greater contribution to the biosynthesis of methionine in germinating rapeseed. |
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