Glycogen debranching enzyme: Difference between revisions

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== Structure and activity ==

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[[File:Hypothesized substraight binding ___location.png|thumb|center|Hypothesized sidechain binding sites|600px]]

The structure of the ''Candida glabrata'' GDE has been reported.<ref>{{cite journal | vauthors = Zhai L, Feng L, Xia L, Yin H, Xiang S | title = Crystal structure of glycogen debranching enzyme and insights into its catalysis and disease-causing mutations | journal = Nature Communications | volume = 7 | pagesarticle-number = 11229 | date = April 2016 | pmid = 27088557 | pmc = 4837477 | doi = 10.1038/ncomms11229 | bibcode = 2016NatCo...711229Z }}</ref> The structure revealed that distinct domains in GDE encode the glucanotransferase and glucosidase activities. Their catalyses are similar to that of alpha-amylase and glucoamylase, respectively. Their active sites are selective towards the respective substrates, ensuring proper activation of GDE. Besides the active sites GDE have additional binding sites for glycogen, which are important for its recruitment to glycogen. Mapping the disease-causing mutations onto the GDE structure provided insights into glycogen storage disease type III.

== Genetic ___location ==

The official name for the gene is "amylo-α-1,6-glucosidase, 4-α-glucanotransferase", with the official symbol AGL. AGL is an autosomal gene found on chromosome 1p21.<ref name=Hondoh/> The AGL gene provides instructions for making several different versions, known as isoforms, of the glycogen debranching enzyme. These isoforms vary by size and are expressed in different tissues, such as liver and muscle. This gene has been studied in great detail, because mutation at this gene is the cause of Glycogen Storage Disease Type III.<ref name=Gene/>

The gene is 85 kb long, has 35 [[exon]]s and encodes for a 7.0 kb mRNA. Translation of the gene begins at exon 3, which encodes for the first 27 amino acids of the AGL gene, because the first two exons (68kb) contain the 5' untranslated region. Exons 4-35 encode the remaining 1505 amino acids of the AGL gene.<ref name= Bao/>

Studies produced by the department of pediatrics at Duke University suggest that the human AGL gene contains at minimum 2 promotor regions, sites where the transcription of the gene begins, that result in differential expression of isoform, different forms of the same protein, mRNAs in a manner that is specific for different tissues.<ref name = Gillard /><ref name=Ding />

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<ref name="MCCarter">{{cite journal | vauthors = McCarter JD, Withers SG | title = Mechanisms of enzymatic glycoside hydrolysis | journal = Current Opinion in Structural Biology | volume = 4 | issue = 6 | pages = 885–892 | date = December 1994 | pmid = 7712292 | doi = 10.1016/0959-440X(94)90271-2 }}</ref>

<ref name="Yamamoto">{{cite journal | vauthors = Yamamoto E, Makino Y, Omichi K | title = Active site mapping of amylo-alpha-1,6-glucosidase in porcine liver glycogen debranching enzyme using fluorogenic 6-O-alpha-glucosyl-maltooligosaccharides | journal = Journal of Biochemistry | volume = 141 | issue = 5 | pages = 627–634 | date = May 2007 | pmid = 17317688 | doi = 10.1093/jb/mvm065 | doi-access = free }}</ref>

<ref name="Hers">{{cite journal | vauthors = Hers HG, Verhue W, Van hoof F | title = The determination of amylo-1,6-glucosidase | journal = European Journal of Biochemistry | volume = 2 | issue = 3 | pages = 257–264 | date = October 1967 | pmid = 6078537 | doi = 10.1111/j.1432-1033.1967.tb00133.x }}</ref>

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<ref name="Molecule">{{cite journal | vauthors = Chiba S | title = Molecular mechanism in alpha-glucosidase and glucoamylase | journal = Bioscience, Biotechnology, and Biochemistry | volume = 61 | issue = 8 | pages = 1233–1239 | date = August 1997 | pmid = 9301101 | doi = 10.1271/bbb.61.1233 | doi-access = free }}</ref>

<ref name="Gene">{{cite web | url = httphttps://ghr.nlm.nihmedlineplus.gov/genetics/gene/AGLagl/ | title = Genes (Genetic Home Reference a service of U.S. National Library of Medicine. | access-date = February 29, 2012 }}</ref>

<ref name="Shen">{{cite journal | vauthors = Shen J, Bao Y, Liu HM, Lee P, Leonard JV, Chen YT | title = Mutations in exon 3 of the glycogen debranching enzyme gene are associated with glycogen storage disease type III that is differentially expressed in liver and muscle | journal = The Journal of Clinical Investigation | volume = 98 | issue = 2 | pages = 352–357 | date = July 1996 | pmid = 8755644 | pmc = 507437 | doi = 10.1172/JCI118799 }}</ref>

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== External links ==

{{Commons category}}

* [https://www.ncbi.nlm.nih.gov/bookshelfbooks/NBK26372/br.fcgi?book=gene&part=gsd3 GeneReviews/NCBI/NIH/UW entry on Glycogen Storage Disease Type III]

* [https://wwwomim.ncbi.nlm.nih.gov/omimorg/search?index=entry&start=1&limit=10&search=232400,+610860,+232400,+610860&sort=score+desc&field=number OMIM entries on Glycogen Storage Disease Type III]

* {{MeSH name|Glycogen+debranching+enzyme}}