This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Carbohydrates Degradation → Polysaccharides Degradation → Starch Degradation|
|Degradation/Utilization/Assimilation → Polymeric Compounds Degradation → Polysaccharides Degradation → Starch Degradation|
Some taxa known to possess this pathway include : Archaeoglobus fulgidus 7324
Expected Taxonomic Range: Archaea
Many organisms including bacteria, fungi, metazoa, and plants can degrade glucose polymers derived from starch or glycogen (see pathways starch degradation II, starch degradation I, glycogen degradation I and glycogen degradation II). Some hyperthermophilic archaea have also been shown to produce starch-degrading enzymes, and pathways for the utilization of starch and its derivatives, such as a cyclodextrin, a maltodextrin, and maltose have been proposed. These hyperthermophilic archaea can utilize starch and its degradation products as primary carbon sources during anaerobic growth. Thermostable starch-degrading enzymes produced by hyperthermophpilic organisms are of industrial interest [Lee06b, Hashimoto01, Labes07, Labes01].
The hyperthermophilic, sulfate-reducing archaeon Archaeoglobus fulgidus 7324 has been shown to degrade starch via a unique pathway involving cyclodextrin intermediates (see a cyclodextrin) as described below in About This Pathway [Labes07, Labes01]. Cyclodextrins (cyclomaltodextrins) are cyclic oligosaccharides composed of α-1,4-linked glucose units. Early literature referred to them as Schardinger dextrins. Cyclodextrins corresponding to 6-12+ glucose units have been characterized (in [DePinto68]) (see α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin). The physicochemical properties of cyclodextrins give them broad applications in the food, cosmetic and pharmaceutical industries (in [Hashimoto01]).
The hyperthermophilic archaeon Pyrococcus furiosus DSM 3638 was shown to degrade starch mainly via maltodextrins in a pathway involving an extracellular amylopullulanase, a transporter, an intracellular 4-α-glucanotransferase, and a maltodextrin phosphorylase. These enzymes produce β-D-glucopyranose and α-D-glucopyranose 1-phosphate that are converted to β-D-glucose 6-phosphate and degraded in pathway glycolysis V (Pyrococcus) ( [Lee06b] and in [Labes07]) (see pathway starch degradation V).
In the hyperthermophilic archaeon Thermococcus sp. B1001 evidence suggested a starch degradation pathway via formation of cyclodextrins from starch extracellularly by a cyclomaltodextrin glucanotransferase, transport of cyclodextrins into the cell, and their degradation by a cyclodextrinase to the end products maltose and α-D-glucopyranose ( [Hashimoto01] and in [Labes07]) (see pathway starch degradation IV).
Among bacteria Escherichia coli cannot utilize starch, but it can metabolize short, linear maltodextrins (see pathway glycogen degradation I). However the enterobacterium Klebsiella oxytoca M5al can utilize starch as a sole source of carbon and energy. Mutant analysis suggested that it metabolizes starch by two pathways. The first was a proposed maltose/maltodextrin pathway involving extracellular degradation of starch by pullulanase and the disproportionation activity of cyclodextrin glucanotransferase to form linear maltodextins. After transport into the cell they are degraded to β-D-glucopyranose and α-D-glucopyranose 1-phosphate by the products of malP, malQ and malZ. The second was a proposed cyclodextrin pathway involving extracellular conversion of starch to cyclodextrins (see a cyclodextrin) by cyclodextrin glucanotransferase, transport into the cell, linearization by cyclodextrinase (CymH) [Feederle96], and further catabolism as in the maltose/maltodextrin pathway [Fiedler96, Pajatsch98].
About This Pathway
Archaeoglobus fulgidus 7324 is a sulfate-reducing, hyperthermophilic archaeon that was shown to utilize starch and sulfate as sources of carbon and energy. Starch was incompletely oxidized to acetate and CO2 via a glycolysis pathway that was enzymatically similar to the glycolysis V (Pyrococcus) pathway shown in the pathway link. Sulfate was reduced to hydrogen sulfide (see pathway sulfate reduction IV (dissimilatory)). The enzymes in this proposed pathway have been characterized as shown here. In contrast, it was noted that another strain, Archaeoglobus fulgidus DSM 4304, does not contain sugar utilization genes and is therefore unable to utilize sugars [Labes07].
This pathway of starch degradation begins with the extracellular production of cyclodextrins (see above) from starch by the membrane-associated enzyme cyclodextrin glucanotransferase. Cyclodextrins are proposed to be taken into the cell by an as yet uncharacterized transport system. Inside the cell they are hydrolyzed to a maltodextrin (maltooligosaccharides) by cyclodextrinase. α-D-glucopyranose 1-phosphate is produced from a maltodextrin (maltooligosaccharides) by maltodextrin phosphorylase. α-D-glucopyranose 1-phosphate is converted by phosphoglucomutase to α-D-glucose 6-phosphate. This compound can enter glycolysis [Labes07], possibly after spontaneous or enzymatic conversion to its epimer β-D-glucose 6-phosphate. Whether the α, β, or both α and β epimers are used depends upon the anomeric specificity of the glycolytic enzyme involved.
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Feederle96: Feederle R, Pajatsch M, Kremmer E, Bock A (1996). "Metabolism of cyclodextrins by Klebsiella oxytoca m5a1: purification and characterisation of a cytoplasmically located cyclodextrinase." Arch Microbiol 165(3);206-12. PMID: 8599539
Hashimoto01: Hashimoto Y, Yamamoto T, Fujiwara S, Takagi M, Imanaka T (2001). "Extracellular synthesis, specific recognition, and intracellular degradation of cyclomaltodextrins by the hyperthermophilic archaeon Thermococcus sp. strain B1001." J Bacteriol 183(17);5050-7. PMID: 11489857
Labes01: Labes A, Schonheit P (2001). "Sugar utilization in the hyperthermophilic, sulfate-reducing archaeon Archaeoglobus fulgidus strain 7324: starch degradation to acetate and CO2 via a modified Embden-Meyerhof pathway and acetyl-CoA synthetase (ADP-forming)." Arch Microbiol 176(5);329-38. PMID: 11702074
Labes07: Labes A, Schonheit P (2007). "Unusual starch degradation pathway via cyclodextrins in the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus strain 7324." J Bacteriol 189(24);8901-13. PMID: 17921308
Lee06b: Lee HS, Shockley KR, Schut GJ, Conners SB, Montero CI, Johnson MR, Chou CJ, Bridger SL, Wigner N, Brehm SD, Jenney FE, Comfort DA, Kelly RM, Adams MW (2006). "Transcriptional and biochemical analysis of starch metabolism in the hyperthermophilic archaeon Pyrococcus furiosus." J Bacteriol 188(6);2115-25. PMID: 16513741
Pajatsch98: Pajatsch M, Gerhart M, Peist R, Horlacher R, Boos W, Bock A (1998). "The periplasmic cyclodextrin binding protein CymE from Klebsiella oxytoca and its role in maltodextrin and cyclodextrin transport." J Bacteriol 180(10);2630-5. PMID: 9573146
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Fu95: Fu L, Bounelis P, Dey N, Browne BL, Marchase RB, Bedwell DM (1995). "The posttranslational modification of phosphoglucomutase is regulated by galactose induction and glucose repression in Saccharomyces cerevisiae." J Bacteriol 177(11);3087-94. PMID: 7768805
Kofler00: Kofler H, Hausler RE, Schulz B, Groner F, Flugge UI, Weber A (2000). "Molecular characterisation of a new mutant allele of the plastid phosphoglucomutase in Arabidopsis, and complementation of the mutant with the wild-type cDNA." Mol Gen Genet 263(6);978-86. PMID: 10954083
Lazarevic05: Lazarevic V, Soldo B, Medico N, Pooley H, Bron S, Karamata D (2005). "Bacillus subtilis alpha-phosphoglucomutase is required for normal cell morphology and biofilm formation." Appl Environ Microbiol 71(1);39-45. PMID: 15640167
Mizanur08a: Mizanur RM, Griffin AK, Pohl NL (2008). "Recombinant production and biochemical characterization of a hyperthermostable alpha-glucan/maltodextrin phosphorylase from Pyrococcus furiosus." Archaea 2(3);169-76. PMID: 19054743
Parche06: Parche S, Beleut M, Rezzonico E, Jacobs D, Arigoni F, Titgemeyer F, Jankovic I (2006). "Lactose-over-glucose preference in Bifidobacterium longum NCC2705: glcP, encoding a glucose transporter, is subject to lactose repression." J Bacteriol 188(4);1260-5. PMID: 16452407
Periappuram00: Periappuram C, Steinhauer L, Barton DL, Taylor DC, Chatson B, Zou J (2000). "The plastidic phosphoglucomutase from Arabidopsis. A reversible enzyme reaction with an important role in metabolic control." Plant Physiol 122(4);1193-9. PMID: 10759515
Qian94: Qian N, Stanley GA, Hahn-Hagerdal B, Radstrom P (1994). "Purification and characterization of two phosphoglucomutases from Lactococcus lactis subsp. lactis and their regulation in maltose- and glucose-utilizing cells." J Bacteriol 176(17);5304-11. PMID: 8071206
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