Journal Article

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

Edurne Baroja-Fernández, Francisco José Muñoz, Takayo Saikusa, Milagros Rodríguez-López, Takashi Akazawa and Javier Pozueta-Romero

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 5, pages 500-509
Published in print May 2003 | ISSN: 0032-0781
Published online May 2003 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcg062
Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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By using barley seeds, developmental changes of ADPglucose (ADPG)-producing sucrose synthase (SS) and ADPG pyrophosphorylase (AGPase) have been compared with those of UDPglucose (UDPG), ADPG, sucrose (Suc) and starch contents. Both ADPG-synthesizing SS and AGPase activity patterns were found to correlate well with those of ADPG and starch contents. Remarkably, however, maximal activities of ADPG-synthesizing SS were found to be several fold higher than those of AGPase throughout seed development, the highest rate of starch accumulation being well accounted for by SS. Kinetic analyses of SS from barley endosperms and potato tubers in the Suc cleavage direction showed similar Km values for ADP and UDP, whereas apparent affinity for Suc was shown to be higher in the presence of UDP than with ADP. Moreover, measurements of transglucosylation activities in starch granules incubated with purified SS, ADP and [U-14C]Suc revealed a low inhibitory effect of UDP. The ADPG and UDPG contents in the transgenic S-112 SS and starch deficient potato mutant [Zrenner et al. (1995) Plant J. 7: 97] were found to be 35% and 30% of those measured in wild-type plants, whereas both glucose-1-phosphate and glucose-6-phosphate contents were found to be normal as compared with those of wild-type plants. The overall results thus strongly support a novel gluconeogenic mechanism reported previously [Pozueta-Romero et al. (1999) Crit. Rev. Plant Sci. 18: 489] wherein SS catalyses directly the de novo production of ADPG linked to starch biosynthesis in heterotrophic tissues of plants.

Keywords: Keywords: Gluconeogenesis — Hordeum vulgare — Solanum tuberosum — Sucrose Synthase (EC 2.4.1.13).; Abbreviations: ADPG, ADPglucose; AGPase, ADPG pyrophosphorylase; DAP, days after pollination; Glc, glucose; G1P, glucose-1-phosphate; G6P, glucose-6-phosphate; HK, hexokinase; PGI, phosphoglucoisomerase; PGM, phosphoglucomutase; Suc, sucrose; SS, sucrose synthase; U, unit; UDPG, UDPglucose; UGPase, UDPG pyrophosphorylase.

Journal Article.  7047 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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