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Titolo:
BIOSYNTHESIS OF (1,3)(1,4)-BETA-GLUCAN AND (1,3)-BETA-GLUCAN IN BARLEY (HORDEUM-VULGARE L) - PROPERTIES OF THE MEMBRANE-BOUND GLUCAN SYNTHASES
Autore:
BECKER M; VINCENT C; REID JSG;
Indirizzi:
UNIV STIRLING,DEPT BIOL & MOLEC SCI STIRLING FK9 4LA SCOTLAND UNIV STIRLING,DEPT BIOL & MOLEC SCI STIRLING FK9 4LA SCOTLAND
Titolo Testata:
Planta
fascicolo: 3, volume: 195, anno: 1995,
pagine: 331 - 338
SICI:
0032-0935(1995)195:3<331:BO(A(I>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
BETA-D-GLUCANS; MAIZE COLEOPTILES; CELL-WALLS; ENDOSPERM; (1->4)-BETA-D-GLUCANS; GRASSES;
Keywords:
CELL WALL BIOSYNTHESIS; HEMICELLULOSE BIOSYNTHESIS; HORDEUM; UDP-GLUCOSE, (1,3)(1,4)-BETA-GLUCAN GLUCOSYL TRANSFERASE [(1,3)(1,4)-BETA-GLUCAN SYNTHASE]; UDP-GLUCOSE, (1,3)-BETA-GLUCAN GLUCOSYL TRANSFERASE [(1,3)-BETA-GLUCAN SYNTHASE]; SYNTHASE];
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
27
Recensione:
Indirizzi per estratti:
Citazione:
M. Becker et al., "BIOSYNTHESIS OF (1,3)(1,4)-BETA-GLUCAN AND (1,3)-BETA-GLUCAN IN BARLEY (HORDEUM-VULGARE L) - PROPERTIES OF THE MEMBRANE-BOUND GLUCAN SYNTHASES", Planta, 195(3), 1995, pp. 331-338

Abstract

Mixed membrane preparations from the coleoptiles and first leaves of young barley (Hordeum vulgare L. cv. Triumph) plants catalysed the synthesis of 55% methanol-insoluble labelled material from UDP-[U-C-14]glucose, the main components of which were identified as (1,3)(1,4)-beta- and (1,3)-beta-D-glucans. The membrane preparations also catalysed the transformation of UDP-glucose into labelled low-molecular-weight products, mainly glucose (by phosphatase action), glucose-1-phosphate (by phosphodiesterase action) and glyco(phospho)lipids (by glycosyltransferase action). The formation of (1,3)(1,4)-beta-glucans, (1,3)-beta-glucans, and the other reactions competing for UDP-glucose, were monitored simultaneously and quantitatively by a novel procedure based on enzymatic analysis, thin-layer chromatography and digital autoradiography. Thus it was possible (i) to optimise conditions to obtain (1,3)(1,4)-beta-glucan synthesis or (1,3)-beta-glucan synthesis in isolation, and (ii) to study the influence of temperature, pH, cofactors, substrate concentration etc. on the (1,3)(1,4)- and (1,3)-beta-glucan synthesis reactions even when both occurred together. The synthesis of both beta-glucans was optimal at 20 degrees C. In Tris-HCl buffer, the pH optima for (1,3)(1,4)-beta-glucan synthesis and (1,3)-beta-glucan synthesis were pH 8.5 and pH 7.0, respectively. Both glucan-synthesis reactions required Mg2+: (1,3)-beta-glucan synthesis was optimal at 2 mM, whereas (1,3)(1,4)-beta-glucan synthesis continued to increase up to 200 mM Mg2+, when the ion was supplied as the sulphate. (1,3)-beta-Glucan synthesis was Ca2+ dependent and this dependence could be abolished byproteinase treatment. The K-m with respect to UDP-glucose was 1.5 mM for (1,3)-beta-glucan synthesis and approximately 1 mM for (1,3)(1,4)-beta-glucan synthesis. The (1,3)(1,4)-beta-glucan formed in vitro had the same ratio of trisaccharide to tetrasaccharide structural blocks irrespective of the experimental conditions used during the synthesis: its enzymatic fragmentation pattern was indistinguishable from that ofbarley endosperm (1,3)(1,4)-beta-glucan. This indicates either a single synthase enzyme, which is responsible for the formation of both linkage types, or two enzymes which are very tightly coupled functionally.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/09/20 alle ore 23:50:42