Note: a dashed line (without arrowheads) between two compound names is meant to imply that the two names are just different instantiations of the same compound -- i.e. one may be a specific name and the other a general name, or they may both represent the same compound in different stages of a polymerization-type pathway. 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.
Synonyms: starch mobilization from cereal endosperm, starch degradation from cereal endosperm
|Superclasses:||Degradation/Utilization/Assimilation → Carbohydrates Degradation → Polysaccharides Degradation → Glycans Degradation|
|Degradation/Utilization/Assimilation → Carbohydrates Degradation → Polysaccharides Degradation → Starch Degradation|
|Degradation/Utilization/Assimilation → Polymeric Compounds Degradation → Polysaccharides Degradation → Glycans Degradation|
|Degradation/Utilization/Assimilation → Polymeric Compounds Degradation → Polysaccharides Degradation → Starch Degradation|
Expected Taxonomic Range: Poaceae
Plants accumulate and mobilize starch in both photosynthetic tissue (leaves) and non-photosynthetic storage tissues (such as tuber and seed endosperm). In leaves, starch is synthesized during the light period and is degraded during the dark period. In storage tissues, starch is degraded during tuber sprouting and seed germinating. Except for seed endosperm where starch degradation occurs in an acellular tissue, starch degradation generally occurs in the plastids (chloroplast of leaves and amyloplast of tubers) where starch accumulates. Isoforms of the starch degradation enzymes are also found and in many cases abundant in extra-plastidic subcellular locations in leaves and tubers. Their physiological functions are not well understood [Zeeman10].
About This Pathway
This pathway represents the starch degradation route present in the endosperm of cereal crops. Many details of the pathway as well as the relative importance of the four types of enzymes that contribute to this process, namely α-amylases, β-amylases, limit dextran debranching enzymes, and α-glucosidases, are still the subject of investigation and debate [Zeeman10, Stanley11].
Unification Links: PlantCyc:PWY-842
Finnie11: Finnie C, Andersen B, Shahpiri A, Svensson B (2011). "Proteomes of the barley aleurone layer: A model system for plant signalling and protein secretion." Proteomics 11(9);1595-605. PMID: 21433287
Rejzek11: Rejzek M, Stevenson CE, Southard AM, Stanley D, Denyer K, Smith AM, Naldrett MJ, Lawson DM, Field RA (2011). "Chemical genetics and cereal starch metabolism: structural basis of the non-covalent and covalent inhibition of barley β-amylase." Mol Biosyst 7(3);718-30. PMID: 21085740
Stanley11: Stanley D, Rejzek M, Naested H, Smedley M, Otero S, Fahy B, Thorpe F, Nash RJ, Harwood W, Svensson B, Denyer K, Field RA, Smith AM (2011). "The role of alpha-glucosidase in germinating barley grains." Plant Physiol 155(2);932-43. PMID: 21098673
Sun91: Sun ZT, Henson CA (1991). "A quantitative assessment of the importance of barley seed alpha-amylase, beta-amylase, debranching enzyme, and alpha-glucosidase in starch degradation." Arch Biochem Biophys 284(2);298-305. PMID: 1824915
Wu02: Wu C, Colleoni C, Myers AM, James MG (2002). "Enzymatic properties and regulation of ZPU1, the maize pullulanase-type starch debranching enzyme." Arch Biochem Biophys 406(1);21-32. PMID: 12234486
Ball11: Ball S, Colleoni C, Cenci U, Raj JN, Tirtiaux C (2011). "The evolution of glycogen and starch metabolism in eukaryotes gives molecular clues to understand the establishment of plastid endosymbiosis." J Exp Bot 62(6);1775-801. PMID: 21220783
Frandsen00: Frandsen TP, Lok F, Mirgorodskaya E, Roepstorff P, Svensson B (2000). "Purification, enzymatic characterization, and nucleotide sequence of a high-isoelectric-point alpha-glucosidase from barley malt." Plant Physiol 123(1);275-86. PMID: 10806244
Naested06: Naested H, Kramhoft B, Lok F, Bojsen K, Yu S, Svensson B (2006). "Production of enzymatically active recombinant full-length barley high pI alpha-glucosidase of glycoside family 31 by high cell-density fermentation of Pichia pastoris and affinity purification." Protein Expr Purif 46(1);56-63. PMID: 16343940
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