10. The enzymic synthesis and degradation of starch. Part XX. The disproportionating enzyme (D-enzyme) of the potato

Peat, Stanley; Whelan, W. J.; Rees, W. R.

doi:10.1039/jr9560000044

Cited by 67 publications

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“…D-enzyme was initially described as an enzyme using and producing soluble oligosaccharides (Peat et al, 1956;Jones and Whelan, 1969). It was assumed to be an integral part of the malto-oligosaccharide assimilation pathway during starch breakdown.…”

Section: D-enzyme Readily Transfers Segments Of Chains Onto Polysacchmentioning

confidence: 99%

“…Absence of all three activities co-segregated with the sta11-1 mutation, which is known to cause abnormal accumulation of oligosaccharides at the expense of starch. To explain these data we propose that D-enzymes function directly in building the amylopectin structure.In plants, the only ␣-1,4 glucanotransferases reported to be present at the time of starch synthesis are collectively called D-enzymes (Peat et al, 1956;Takaha et al, 1993). D-enzymes act on soluble oligosaccharides at least three Glc residues long (maltotriose) and disproportionate them into oligosaccharides of various lengths at the expense of Glc formation.…”

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“…In plants, the only ␣-1,4 glucanotransferases reported to be present at the time of starch synthesis are collectively called D-enzymes (Peat et al, 1956;Takaha et al, 1993). D-enzymes act on soluble oligosaccharides at least three Glc residues long (maltotriose) and disproportionate them into oligosaccharides of various lengths at the expense of Glc formation.…”

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Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis1

et al. 1999

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Plant ␣-1,4 glucanotransferases (disproportionating enzymes, or D-enzymes) transfer glucan chains among oligosaccharides with the concomitant release of glucose (Glc). Analysis of Chlamydomonas reinhardtii sta11-1 mutants revealed a correlation between a D-enzyme deficiency and specific alterations in amylopectin structure and starch biosynthesis, thereby suggesting previously unknown biosynthetic functions. This study characterized the biochemical activities of the ␣-1,4 glucanotransferase that is deficient in sta11-1 mutants. The enzyme exhibited the glucan transfer and Glc production activities that define D-enzymes. D-enzyme also transferred glucans among the outer chains of amylopectin (using the polysaccharide chains as both donor and acceptor) and from malto-oligosaccharides into the outer chains of either amylopectin or glycogen. In contrast to transfer among oligosaccharides, which occurs readily with maltotriose, transfer into polysaccharide required longer donor molecules. All three enzymatic activities, evolution of Glc from oligosaccharides, glucan transfer from oligosaccharides into polysaccharides, and transfer among polysaccharide outer chains, were evident in a single 62-kD band. Absence of all three activities co-segregated with the sta11-1 mutation, which is known to cause abnormal accumulation of oligosaccharides at the expense of starch. To explain these data we propose that D-enzymes function directly in building the amylopectin structure.In plants, the only ␣-1,4 glucanotransferases reported to be present at the time of starch synthesis are collectively called D-enzymes (Peat et al., 1956;Takaha et al., 1993). D-enzymes act on soluble oligosaccharides at least three Glc residues long (maltotriose) and disproportionate them into oligosaccharides of various lengths at the expense of Glc formation. In such a reaction an ␣-1,4 linkage is cleaved from a donor unbranched oligosaccharide of at least three Glc residues, and the resulting chain segment is transferred to another acceptor glucan, creating a novel ␣-1,4 linkage. Maltosyl residues are often transferred as a result of D-enzyme action, but maltose itself is not a product of the reaction. However, both Glc and maltose can be used as acceptors (Jones and Whelan, 1969). It is known that in Arabidopsis leaves, D-enzyme is the major maltotriosemetabolizing enzyme present (Lin and Preiss, 1988;Zeeman et al., 1998). The presence of this activity during potato tuber development has led investigators to suggest that D-enzyme might be required for some specific aspect of starch biosynthesis (Takaha et al., 1993). Like a few other glucanotransferases, such as branching enzyme (Takaha et al., 1996a), D-enzyme has been recently shown to lead to the formation of cyclic compounds after prolonged incubation of both amylose and amylopectin with high amounts of pure activity (Takaha et al., 1996b(Takaha et al., , 1998. It is not known if this property relates to the physiological function of this enzyme. D-enzyme is believed to be part of the starch degra...

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Section: D-enzyme Readily Transfers Segments Of Chains Onto Polysacchmentioning

confidence: 99%

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confidence: 99%

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Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis1

et al. 1999

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“…Amylomaltases are 4-␣-glucanotransferase enzymes (1)(2)(3)(4) that are structurally and mechanistically related to ␣-amylases (family 13 of the glycoside hydrolases or GH13) (5-7) despite their classification in a separate glycoside hydrolase family (glycoside hydrolase family 77). However, amylomaltases almost exclusively catalyze transglycosylation reactions, whereas ␣-amylase-like enzymes mostly catalyze hydrolysis.…”

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Three-way Stabilization of the Covalent Intermediate in Amylomaltase, an α-Amylase-like Transglycosylase

Barends

Bultema

Kaper

et al. 2007

Journal of Biological Chemistry

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Amylomaltases are glycosyl hydrolases belonging to glycoside hydrolase family 77 that are capable of the synthesis of large cyclic glucans and the disproportionation of oligosaccharides. Using protein crystallography, we have generated a flip book movie of the amylomaltase catalytic cycle in atomic detail. The structures include a covalent glycosyl enzyme intermediate and a covalent intermediate in complex with an analogue of a cosubstrate and show how the structures of both enzyme and substrate respond to the changes required by the catalytic cycle as it proceeds. Notably, the catalytic nucleophile changes conformation dramatically during the reaction. Also, Gln-256 on the 250s loop is involved in orienting the substrate in the ؉1 site. The absence of a suitable base in the covalent intermediate structure explains the low hydrolysis activity.Amylomaltases are 4-␣-glucanotransferase enzymes (1-4) that are structurally and mechanistically related to ␣-amylases (family 13 of the glycoside hydrolases or GH13) (5-7) despite their classification in a separate glycoside hydrolase family (glycoside hydrolase family 77). However, amylomaltases almost exclusively catalyze transglycosylation reactions, whereas ␣-amylase-like enzymes mostly catalyze hydrolysis. As a result, the amylomaltases perform so-called disproportionation reactions, the net effect of which is that two amylose chains of certain lengths react in such a way that one of the chains (the "donor") becomes shorter and the other one (the "acceptor") longer as shown in Reaction 1.Instead of using two different sugar chains for this reaction, the enzyme can also take the non-reducing end of the donor substrate as the acceptor substrate, which results in the formation of a cyclic glucan product of at least 16 glucose units (8 -11). These properties, amylose disproportionation and the synthesis of large cyclic glucans, make these enzymes interesting biocatalysts for the synthesis of valuable fine chemicals and pharmaceutically important materials (12)(13)(14). Over the years, several incisive studies have contributed to our current understanding of catalysis by ␣-amylase-type enzymes. Importantly, a structure of a covalent reaction intermediate, obtained by Uitdehaag et al. (15), provided a detailed look into the active site, showing among other things how the (mutated) acid/base catalyst is poised to activate a water molecule for attack on the C 1 carbon atom. Since then, two other examples of covalent glycosyl enzyme intermediate structures of ␣-amylase-type enzymes have been published (16,17). These structures provided insight into the hydrolysis mechanism, i.e. in the way in which a covalent intermediate is attacked by a water molecule. Three conserved carboxylic acid residues play a central role in the catalytic mechanism (15, 18 -20). The first carboxylic acid residue acts as an acid/base catalyst that protonates the oxygen atom of the scissile glycosidic bond. Simultaneously, the C 1 carbon atom is attacked by the second carboxylate, the nucleophile, which...

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“…We purified and characterized the enzyme, and found that it was 4-a-glucanotransferase on the basis of the results obtained. 4-a-Glucanotransferase was first found in potato tubers by Peat et al (1956) and called disproportionating enzyme (D-enzyme). Enzymes with similar functions have been reported: Streptococcus mitis transglucosylase (Walker, 1966); Escherichia coli amylomaltase (Palmer et al, 1976), and D-enzyme from plant leaves (Lin and Preiss, 1988).…”

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4‐α‐Glucanotransferase from the Hyperthermophilic Archaeon Thermococcus Litoralis

Jeon

Taguchi

Sakai

et al. 1997

European Journal of Biochemistry

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4-a-Glucanotransferase was purified from cells of Thermococcus litoralis, a hyperthermophilic archaeon. The molecular mass of the enzyme was estimated to be approximately 87 kDa by gel filtration. The optimal temperature for its activity was 90 "C. The enzyme catalyzed the transglycosylation of maltooligosaccharides, yielding maltooligosaccharides of various lengths and glucose. When maltoheptaose was used as the substrate, glucoamylase-resistant and glucoamylase-sensitive saccharides were produced.On incubation of amylose with the 7: litoralis enzyme, glucoamylase-resistant but a-amylase-sensitive molecules were produced, but the amount of reducing sugar showed only slight increases. These results indicate that the 7: litoralis enzyme catalyzes not only intermolecular transglycosylation to produce linear a-1,4-glucan, but also intramolecular transglycosylation to produce cyclic a-1 ,4-glucan (cycloamylose), similarly to potato 4-a-glucanotransferase (called disproportionating enzyme). The gene encoding the 7: litoralis 4-a-glucanotransferase was cloned, sequenced and expressed in Escherichia coli. The nucleotide sequence of the gene encoded a 659-amino acid protein with a calculated molecular mass of 77 883 Da.The amino acid sequence of the 7: litoralis enzyme showed high similarity with those of a-amylases of Pyrococcus furiosus, a hyperthermophilic archaeon, and Dictyoglomus thermophilum, an extremely thermophilic bacterium, but little similarity with those of other known 4-a-glucanotransferases.Keywords: hyperthermophilic archaeon ; Thermococcus litoralis ; 4-a-glucanotransferase ; cyclic a-1,4-glucan; gene cloning.In recent years several hyperthermophilic archaea, capable of growing anaerobically, even at IOO"C, have been isolated from submarine volcanic areas (Fiala and Stetter, 1986;Kelly and Deming, 1988). One of the characteristics of these organisms is their ability to utilize complex saccharolytic substrates, such as starch and glycogen, as carbon and energy sources. Pyrococcus furiosus, a marine hyperthermophile that grows optimally at 98"C, is probably the best-characterized member of the thermophilic archaea. The metabolism of a variety of complex substrates by P: furiosus begins with their hydrolysis by a series of extracellular amylolytic enzymes exhibiting amylase and pullulanase activities (Koch et al., 1990;Brown et al., 1990). The ability to digest complex saccharides is also characteristic of Thermococcus litoralis, a hyperthermophilic marine archaeon with an optimal growth temperature of 85°C (Neuner et al., 1990). It appears to resemble R furiosus in many aspects of growth and metabolism, but it has not been well characterized.We searched for sugar-metabolizing enzymes produced by hyperthermophilic archaea, and in a cell-free extract of 7: litoCorrespondence to H . Matsuzawa,

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10. The enzymic synthesis and degradation of starch. Part XX. The disproportionating enzyme (D-enzyme) of the potato

Cited by 67 publications

References 0 publications

Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis1

Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis1

Three-way Stabilization of the Covalent Intermediate in Amylomaltase, an α-Amylase-like Transglycosylase

4‐α‐Glucanotransferase from the Hyperthermophilic Archaeon Thermococcus Litoralis

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