title: The formation of sulphur-containing amino acids in germinating seeds of rape (Brassica napus L.).
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.
mesh_terms: D000596:Amino Acids / Q000096:biosynthesis*; D002247:Carbon Isotopes; D003540:Cystathionine / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism; D006714:Homoserine / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D013440:Sulfides; D013460:Sulfur Isotopes
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D013440:Sulfides; D013460:Sulfur Isotopes; D006710:Homocysteine; D003540:Cystathionine; D006714:Homoserine; D008715:Methionine; D003545:Cysteine