The action of starch synthase II on 6′′′‐α‐maltotriosyl‐maltohexaose comprising the branch point of amylopectin

Damager, Iben; Denyer, Kay; Motawia, Mohammed Saddik; Møller, Birger Lindberg; Blennow, Andreas

doi:10.1046/j.1432-1327.2001.02413.x

Cited by 18 publications

(13 citation statements)

References 34 publications

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“…All of the added putative primers were found to inhibit starch synthesis; the inhibition increased, as the concentrations of the putative primers were increased (see, Figure 1 for the inhibition of maize starch by maltose and maltotriose), contrary to what would be expected for the synthesis of starch by the addition of glucose to primers. The putative primers did undergo a reaction to primarily form the next higher homologue, similar to what previously had been observed by Damager et al (2001).…”

Section: G-p G-g-g-g- +supporting

confidence: 78%

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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Section: G-p G-g-g-g- +supporting

confidence: 78%

Mechanisms involved in the biosynthesis of polysaccharides

Robyt

2008

Biologia

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“…It is generally known that plant SS isozymes exhibit high activities toward various branched glucans including amylopectin and glycogen while the activities for linear MOS and amylose are very low Damager et al 2001;Imparl-Radosevich et al 2003;Senoura et al 2007;Nakamura et al 2014). It is also well known that SSI and SSII are markedly activated by high concentrations ( 0.3 M) of citrate (Ozbun et al 1971b;Hawker et al 1974;Boyer and Preiss 1979;Pollock and Preiss 1980;Senoura et al 2007;Nakamura et al 2014) (for other properties of SS, see review by Fujita and Nakamura 2012).…”

Section: Multiple Ss Isozymesmentioning

confidence: 99%

Biosynthesis of Reserve Starch

Nakamura

2015

Starch

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Plants have developed two distinct starch biosynthetic systems composed of over 30 kinds of enzymatic reaction network in photosynthetic and nonphotosynthetic cells. Higher plants have also evolved a process in which cells can accumulate huge amounts of starch as granules inside the amyloplast of the reserve organs. Primarily the coordinated expression of several sets of distinct isozymes with specific enzymatic properties enables plant cells to synthesize starch with distinct fine structure and form the starch granules with specific semicrystalline structure, granular morphology, and physicochemical properties in plastids. This chapter overviews the current status of our understanding of metabolic regulation of starch biosynthesis in reserve organs by focusing on functions of individual isozymes examined by numerous in vivo and in vitro studies that have been performed to reveal how individual isozymes contribute to the synthesis of the reserve starch. The results raised the high possibility that at least some isozymes have multiple functions in starch biosynthesis under different conditions depending on the presence of various glucans and interaction/association with other enzymes. The features of starch biosynthetic process in plant tissues are also discussed with emphasis on the biochemical mechanism(s) underlying the coordinate actions among various enzymes.

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“…Much later, Damager et al 16, studied the reaction of a low‐amylose, pea mutant lam starch granules, containing granule bound SSII with maltotriose and maltohexaose and a branched nine‐carbon maltodextrin, 6 III ‐α‐maltotriosyl maltohexaose, as putative primers. They found that the maltodextrins did not give the synthesis of starch chains by reaction with starch‐synthase and only added one or two glucose units to the nonreducing‐ends of the maltodextrins, and only one glucose unit was added to each of the two nonreducing‐ends of the branched, 6 III ‐α‐maltotriosyl maltohexaose, which was not further elongated to give starch synthesis.…”

Section: Historical Background From 1940 To 1966mentioning

confidence: 99%

Evolution of the development of how starch is biosynthesized

Robyt¹,

Mukerjea²

2012

Starch Stärke

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In 1940, C.S. Hanes found that potato phosphorylase transferred a few two to three glucose units from α‐D‐Glc‐1‐P to the nonreducing‐ends of starch. Starting with only α‐D‐Glc‐1‐P and phosphorylase, there was no reaction and a starch‐primer was required for reaction. In 1960, Leloir and coworkers incubated starch granules with ADP‐[14C]Glc and found that 14C‐starch was synthesized. Reaction with β‐amylase gave 14C‐maltose from the nonreducing‐ends and it was assumed that the glucose was being added to the nonreducing‐ends of a primer. Mukerjea and Robyt pulsed and chased starch‐granules with ADP‐[14C]Glc and ADPGlc, and found on reduction and hydrolysis of the 14C‐starch, 14C‐D‐glucitol was obtained, indicating that glucose was added to the reducing‐ends of growing starch‐chains. They obtained highly purified, starch‐synthase that was shown to be free of starch‐primers and gave de novo synthesis, with the addition of glucose to the reducing‐ends. They also found 61 papers from 1964 to 2012 that used 50–100 mM Tris‐type buffers with starch‐synthase and had to add putative‐primers to obtain activity. Mukerjea et al. showed that 25 mM Tris‐type buffers, completely inhibited starch‐synthase. Addition of 10 mg/mL putative‐primers, glycogen or maltotetraose, gave partial (8–57%) reversal of the inhibition. The putative‐primers were activators and not primers; however, their use perpetuated the primer myth for 50 years. A hypothesis is developed, as to how starch granules are initiated and grow in vivo.

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The action of starch synthase II on 6′′′‐α‐maltotriosyl‐maltohexaose comprising the branch point of amylopectin

Cited by 18 publications

References 34 publications

Mechanisms involved in the biosynthesis of polysaccharides

Mechanisms involved in the biosynthesis of polysaccharides

Biosynthesis of Reserve Starch

Evolution of the development of how starch is biosynthesized

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