Interaction with amylopectin influences the ability of granule-bound starch synthase I to elongate malto-oligosaccharides

Denyer, Kay; Waite, Darren; Edwards, Anne; Martin, Cathie; Smith, Alison M.

doi:10.1042/bj3420647

Cited by 34 publications

(12 citation statements)

References 25 publications

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“…Like potato GBSSI, pea GBSSIb exhibited a lag in initiating glucan synthesis of 1 to 4 min, depending on amylopectin concentration (data not shown). GBSSIb showed processive rather than distributive activity (the enzyme preferentially added successive Glc units to a single glucan chain rather than to different chains) when supplied with 100 mM maltotriose and 2.5 mg/mL amylopectin (data not shown), as does potato GBSSI (Denyer et al, 1999;Edwards et al, 1999a).…”

Section: Expression Of Gbssia and Gbssib In E Colimentioning

confidence: 99%

“…The mechanisms by which different isoforms of starch synthase catalyze the same reaction and yet generate polymer variation are not fully understood, but there is increasing evidence to suggest that isoform localization within the plastid and fundamental differences in kinetics and reaction mechanisms are important determinants of product specificity Denyer et al, 1999;Edwards et al, 1999a;Imparl-Radosevich et al, 1999;Commuri and Keeling, 2001). Furthermore, recent work has suggested that GBSSI, like the soluble starch synthases, may exist as more than one isoform.…”

Section: Introductionmentioning

confidence: 99%

“…Unless stated otherwise, 0.23 kBq of ADP-U-14 C-Glc was used per 100-L reaction. Assays were incubated at 25ЊC for 20 min, terminated by heating at 90ЊC for 2 min, and processed by either the methanol/KCl method or the resin method (Denyer et al, 1999). All assays and controls were duplicated.…”

Section: Starch Synthase Assaysmentioning

confidence: 99%

“…Assays contained 50 L (1 to 2 mg) of starch, 1 mM ADP-Glc, 5 mg/mL amylopectin, and 100 mM maltotriose and were processed by the methanol/KCl method (Denyer et al, 1999).…”

Section: Potato Starch Granulesmentioning

confidence: 99%

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Discrete Forms of Amylose Are Synthesized by Isoforms of GBSSI in Pea[W]

Edwards

Vincken²,

Suurs³

et al. 2002

The Plant Cell

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Amyloses with distinct molecular masses are found in the starch of pea embryos compared with the starch of pea leaves. In pea embryos, a granule-bound starch synthase protein (GBSSIa) is required for the synthesis of a significant portion of the amylose. However, this protein seems to be insignificant in the synthesis of amylose in pea leaves. cDNA clones encoding a second isoform of GBSSI, GBSSIb, have been isolated from pea leaves. Comparison of GBSSIa and GBSSIb activities shows them to have distinct properties. These differences have been confirmed by the expression of GBSSIa and GBSSIb in the amylose-free mutant of potato. GBSSIa and GBSSIb make distinct forms of amylose that differ in their molecular mass. These differences in product specificity, coupled with differences in the tissues in which GBSSIa and GBSSIb are most active, explain the distinct forms of amylose found in different tissues of pea. The shorter form of amylose formed by GBSSIa confers less susceptibility to the retrogradation of starch pastes than the amylose formed by GBSSIb. The product specificity of GBSSIa could provide beneficial attributes to starches for food and nonfood uses.

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Section: Expression Of Gbssia and Gbssib In E Colimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Starch Synthase Assaysmentioning

confidence: 99%

“…Assays contained 50 L (1 to 2 mg) of starch, 1 mM ADP-Glc, 5 mg/mL amylopectin, and 100 mM maltotriose and were processed by the methanol/KCl method (Denyer et al, 1999).…”

Section: Potato Starch Granulesmentioning

confidence: 99%

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Discrete Forms of Amylose Are Synthesized by Isoforms of GBSSI in Pea[W]

Edwards

Vincken²,

Suurs³

et al. 2002

The Plant Cell

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“…In another study, higher homologues beyond the first homologue were produced up to degree of polymerization (d.p.) 6, but in much lower, exponentially decreasing amounts (Denyer et al 1999). Mukerjea & Robyt (2005) examined the effect of adding the putative primers (maltose, maltotriose, and d.p.…”

Section: G-p G-g-g-g- +mentioning

confidence: 99%

Mechanisms involved in the biosynthesis of polysaccharides

Robyt

2008

Biologia

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Abstract:The mechanisms for the biosynthesis of three polysaccharides are presented: (i) starch synthesized by starch synthase and adenosine diphospho glucose; (ii) dextran synthesized by Leuconostoc mesenteroides B-512FMC dextransucrase and sucrose; and (iii) Acetobacter xylinum cellulose synthesized by cellulose synthase, uridine diphospho glucose, and bactoprenol phosphate. All three enzymes were pulsed with substrates, containing 14 C-glucose and chased with the same nonlabeled substrates. When the polysaccharides were isolated, reduced, and hydrolyzed, the pulsed reactions gave 14 C-glucitol, which was significantly decreased in the chase reaction. These experiments definitively show that all three polysaccharides are biosynthesized by the addition of glucose to the reducing-ends of the growing polysaccharides and not by the addition to the nonreducing-ends of primers. Additional evidence indicates that glucose and the polysaccharides are covalently attached to the active-sites of the enzymes. A two catalytic-site insertion mechanism at one active-site is proposed for the biosyntheses. Two of the polysaccharides are α-linked glucans, starch and dextran, and cellulose is a β-linked glucan, known for several years to require a bactoprenol lipid phosphate intermediate. It is shown how this intermediate is involved in determining that β-linkages are synthesized. Other β-linked polysaccharides: bacterial cell wall peptidomurein, Salmonella O-antigen polysaccharide, and Xanthanomonas camprestris xanthan, are heteropolysaccharides, with the later two also being hetero-linked polysaccharides, with the β-linkage at the reducing-end of the repeating unit. All three require bactoprenol lipid phosphate intermediates and are biosynthesized by the addition of the repeating units to the reducing-end of a growing polysaccharide chain, with the formation of a β-linkage.Key words: starch; dextran; cellulose; starch synthase; dextransucrase; cellulose synthase; reducing-end synthesis.Abbreviations: ADPGlc, adenosine diphospho glucose; CP, conversion period, which is the theoretical time necessary to convert the substrate into product for the amount of enzyme present; d.p., degree of polymerization; α-Glc-1-P, α-Dglucose-1-phosphate; Pi, inorganic phosphate; UDPGlc, uridine diphospho glucose.

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