title: Chemical synthesis of methyl 6'-alpha-maltosyl-alpha-maltotrioside and its use for investigation of the action of starch synthase II.
abstract: The branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside was chemically synthesised and investigated as a primer for particulate starch synthase II (SSII) using starch granules prepared from the low-amylose pea mutant lam as the enzyme source. For chemical synthesis, the trichloroacetimidate activation method was used to synthesise methyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl-(1-->4)]-O-(2,3-di-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, which was then debenzylated to provide the desired branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside as documented by 1H and 13C NMR spectroscopy. Using a large excess of the maltoside, the pentasaccharide was tested as a substrate for starch synthase II (SSII). Both of the non-reducing ends of methyl 6'-alpha-maltosyl-alpha-maltotrioside were extended equally resulting in two hexasaccharide products in nearly equal amounts. Thus, SSII catalyses an equimolar and non-processive elongation reaction of this substrate. Accordingly, the presence of the alpha-1,6 linkages does not dictate a specific structure of the pentasaccharide in which only one of the two non-reducing ends are available for extension.
authors.affiliation: Department of Plant Biology, Carbohydrate Chemistry Group at Plant Biochemistry Laboratory, The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: Iben
authors.initials: I
authors.lastname: Damager
authors.forename: Carl Erik
authors.initials: CE
authors.lastname: Olsen
authors.forename: Andreas
authors.initials: A
authors.lastname: Blennow
authors.forename: Kay
authors.initials: K
authors.lastname: Denyer
authors.forename: Birger Lindberg
authors.initials: BL
authors.lastname: Møller
authors.forename: Mohammed Saddik
authors.initials: MS
authors.lastname: Motawia
mesh_terms: D002384:Catalysis; D004187:Disaccharides / Q000138:chemical synthesis* / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008320:Maltose / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000378:metabolism; D009844:Oligosaccharides / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D010940:Plant Proteins; D013214:Starch Synthase / Q000378:metabolism*; D013379:Substrate Specificity; D014312:Trisaccharides / Q000138:chemical synthesis* / Q000378:metabolism
chemical_list: D004187:Disaccharides; D009844:Oligosaccharides; D010940:Plant Proteins; D014312:Trisaccharides; C477982:methyl 6'-alpha-maltosyl-alpha-maltotrioside; D008320:Maltose; C111377:starch synthase II; D013214:Starch Synthase; D005947:Glucose