The Mechanism of Synthesis of a Mixed-Linkage (1→3),(1→4)β-<scp>d</scp>-Glucan in Maize. Evidence for Multiple Sites of Glucosyl Transfer in the Synthase Complex1

DOI PDF 被引用文献4件
  • Marcos S. Buckeridge
    Instituto de Botânica, Secão de Fisiologia e Bioquı́mica Plantas, Caixa Postal 4005, CEP–01061970, São Paulo, SP Brazil (M.S.B.)
  • Claudia E. Vergara
    Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907–1155 (C.E.V., N.C.C.)
  • Nicholas C. Carpita
    Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907–1155 (C.E.V., N.C.C.)

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<jats:title>Abstract</jats:title> <jats:p>We examined the mechanism of synthesis in vitro of (1→3),(1→4)β-d-glucan (β-glucan), a growth-specific cell wall polysaccharide found in grasses and cereals. β-Glucan is composed primarily of cellotriosyl and cellotetraosyl units linked by single (1→3)β-linkages. The ratio of cellotriosyl and cellotetraosyl units in the native polymer is strictly controlled at between 2 and 3 in all grasses, whereas the ratios of these units in β-glucan formed in vitro vary from 1.5 with 5 μm UDP-glucose (Glc) to over 11 with 30 mmsubstrate. These results support a model in which three sites of glycosyl transfer occur within the synthase complex to produce the cellobiosyl-(1→3)-d-glucosyl units. We propose that failure to fill one of the sites results in the iterative addition of one or more cellobiosyl units to produce the longer cellodextrin units in the polymer. Variations in the UDP-Glc concentration in excised maize (Zea mays) coleoptiles did not result in wide variations in the ratios of cellotriosyl and cellotetraosyl units in β-glucan synthesized in vivo, indicating that other factors control delivery of UDP-Glc to the synthase. In maize sucrose synthase is enriched in Golgi membranes and plasma membranes and may be involved in the control of substrate delivery to β-glucan synthase and cellulose synthase.</jats:p>

収録刊行物

  • Plant Physiology

    Plant Physiology 120 (4), 1105-1116, 1999-08-01

    Oxford University Press (OUP)

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