title: Major proteins of yam bean tubers.
abstract: The tuberous roots of the Mexican yam bean, jicama, (Pachyrhizus erosus L. Urban) contained large quantities of two acidic glycoproteins which accounted for more than 70% of the total soluble proteins (about 3 g per 100 g of tuber on a dry weight basis). The two major proteins, tentatively named YBG1 and YBG2, had apparent M(r)s of 28,000 and 26,000, respectively, by SDS-PAGE. A third protein named YBP22 which accounted for 2-5% of the total soluble proteins had an M(r) of 22,000. YBG1 and YBG2 exhibited great similarity on the basis of their amino acid composition and had identical N-terminal amino acid sequences. The first 23 amino acids in the N-terminal region of YBG2 were DDLPDYVDWRDYGAVTRIKNQGQ which showed strong homology with the papain class of cysteine proteases. YBG1 and YBG2 were found to bind to a Concanavalin A-Sepharose column and were also stained positively by a sensitive glycoprotein stain. Both glycoproteins exhibited cysteine proteolytic activity. In contrast, YBP22 showed sequence homology with several known protease inhibitors, and a polyclonal antibody raised against this protein cross reacted with soybean trypsin inhibitor.
authors.affiliation: Department of Biochemistry, Faculty of Medical Sciences, University of the West Indies, St. Augustine, Trinidad and Tobago.
authors.forename: A V
authors.initials: AV
authors.lastname: Gomes
authors.forename: G
authors.initials: G
authors.lastname: Sirju-Charran
authors.forename: J A
authors.initials: JA
authors.lastname: Barnes
mesh_terms: D000595:Amino Acid Sequence; D007887:Fabaceae / Q000737:chemistry*; D006023:Glycoproteins / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D018517:Plant Roots / Q000737:chemistry; D010946:Plants, Medicinal; D017386:Sequence Homology, Amino Acid
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins