title: Seed storage protein deficiency improves sulfur amino acid content in common bean (Phaseolus vulgaris L.): redirection of sulfur from gamma-glutamyl-S-methyl-cysteine.
abstract: The contents of sulfur amino acids in seeds of common bean ( Phaseolus vulgaris L.) are suboptimal for nutrition. They accumulate large amounts of a gamma-glutamyl dipeptide of S-methyl-cysteine, a nonprotein amino acid that cannot substitute for methionine or cysteine in the diet. Protein accumulation and amino acid composition were characterized in three genetically related lines integrating a progressive deficiency in major seed storage proteins, phaseolin, phytohemagglutinin, and arcelin. Nitrogen, carbon, and sulfur contents were comparable among the three lines. The contents of S-methyl-cysteine and gamma-glutamyl-S-methyl-cysteine were progressively reduced in the mutants. Sulfur was shifted predominantly to the protein cysteine pool, while total methionine was only slightly elevated. Methionine and cystine contents (mg per g protein) were increased by up to ca. 40%, to levels slightly above FAO guidelines on amino acid requirements for human nutrition. These findings may be useful to improve the nutritional quality of common bean.
authors.affiliation: Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, 1391 Sandford Street, London, Ontario, N5V 4T3, Canada.
authors.forename: Meghan
authors.initials: M
authors.lastname: Taylor
authors.forename: Ralph
authors.initials: R
authors.lastname: Chapman
authors.forename: Ronald
authors.initials: R
authors.lastname: Beyaert
authors.forename: Cinta
authors.initials: C
authors.lastname: Hernández-Sebastià
authors.forename: Frédéric
authors.initials: F
authors.lastname: Marsolais
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000603:Amino Acids, Sulfur / Q000032:analysis*; D003545:Cysteine / Q000031:analogs & derivatives / Q000737:chemistry; D004151:Dipeptides / Q000737:chemistry*; D009753:Nutritive Value; D027805:Phaseolus / Q000737:chemistry* / Q000235:genetics; D010940:Plant Proteins / Q000032:analysis*; D012639:Seeds / Q000737:chemistry*; D013455:Sulfur / Q000032:analysis*
chemical_list: D000596:Amino Acids; D000603:Amino Acids, Sulfur; D004151:Dipeptides; D010940:Plant Proteins; C531026:gamma-glutamyl-S-methylcysteine; D013455:Sulfur; C008425:S-methylcysteine; D003545:Cysteine