Starch biosynthesis: mechanism for the elongation of starch chains

Mukerjea, Rupendra; Yu, Liangli; Robyt, John F.

doi:10.1016/s0008-6215(02)00067-8

Cited by 39 publications

(33 citation statements)

References 28 publications

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“…The first set of experiments was a pulse with ADP-[ 14 C]Glc and a chase with nonlabeled ADPGlc of eight different kinds of starch granules. 12 The pulsed granules gave starch chains that on reduction with NaBH 4 and hydrolysis gave 14 C-D-glucitol and 14 C-D-glucose, and the chase experiments gave a significant decrease in the amount of label in D-glucitol. These experiments indicated that the starch chains were being elongated from the reducing end and not from the nonreducing ends of primers.…”

Section: Introductionmentioning

confidence: 96%

“…Because of these problems and the lack of definitive experiments supporting the nonreducing end primer elongation of starch chains, Mukerjea and Robyt [12][13][14] carried out a number of experiments to test the nonreducing end primer mechanism. The first set of experiments was a pulse with ADP-[ 14 C]Glc and a chase with nonlabeled ADPGlc of eight different kinds of starch granules.…”

Section: Introductionmentioning

confidence: 99%

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Starch biosynthesis: experiments on how starch granules grow in vivo

Mukerjea

Robyt

2009

Carbohydrate Research

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Starch biosynthesis: experiments on how starch granules grow in vivo

Mukerjea

Robyt

2009

Carbohydrate Research

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“…After the starches were solubilized, reduced with NaBH 4 , and completely hydrolyzed by glucoamylase, the pulsed starches gave 14 C-glucitol and the chased starches gave a significant decrease in 14 C-glucitol (Table 1). These experiments definitely showed that glucose was being added to the reducing-ends of the growing starch chains, as it would have been impossible to obtain and chase 14 C-glucitol if the glucose was being added to the nonreducing-ends of primers (Mukerjea et al 2002). In this same study, experiments also showed that a glucose and a starch chain were covalently linked to the active-site of starch synthase, during chain elongation.…”

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

confidence: 85%

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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“…The biosynthesis of both starch amylose and amylopectin from saccharose proceeds via ADP-D-Glc (MUKERJEA et al 2002;JAMES et al 2003;VANDEPUTTE & DELCOURT 2004). Sucrose synthase (EC 2.4.1.13) converts saccharose into D-fructose and UDP-D-Glc.…”

Section: Starch and Glycogenmentioning

confidence: 99%

Biosynthesis of food constituents: Saccharides. 2. Polysaccharides - a review

Velı́šek¹,

Cejpek²

2005

Czech J. Food Sci.

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This review article gives a survey of the selected principal biosynthetic pathways that lead to the most important polysaccharides occurring in foods and in food raw materials and informs non-specialist readers about new scientific advances as reported in recently published papers. Subdivision of the topic is predominantly done via biosynthesis and includes reserve polysaccharides (starch and glycogen, fructans), plant cell wall polysaccharides (cellulose and callose, pectin), and animal polysaccharides (chitin and glycosaminoglycans). Extensively used are the reaction schemes, sequences, and mechanisms with the enzymes involved and detailed explanations using sound chemical principles and mechanisms.

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Starch biosynthesis: mechanism for the elongation of starch chains

Cited by 39 publications

References 28 publications

Starch biosynthesis: experiments on how starch granules grow in vivo

Starch biosynthesis: experiments on how starch granules grow in vivo

Mechanisms involved in the biosynthesis of polysaccharides

Biosynthesis of food constituents: Saccharides. 2. Polysaccharides - a review

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