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Glycoside Hydrolase Family 91

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  • If you are interested in contributing to CAZypedia, please see the 10th anniversary publication [1] and this page for an overview of the content and mission of our community-driven resource. Future authors of CAZypedia can include the CAZypedia article [1] and cite individual pages in their curricula vitae to reflect their contribution.
  • Until this CAZypedia page is completed, current information on the composition of this family is available via the corresponding page of the CAZy database [2]:


  1. CAZypedia Consortium (2018). Ten years of CAZypedia: a living encyclopedia of carbohydrate-active enzymes. Glycobiology. 2018;28(1):3-8. DOI:10.1093/glycob/cwx089 | PubMed ID:29040563 [CAZypedia2018]
  2. Lombard V, Golaconda Ramulu H, Drula E, Coutinho PM, and Henrissat B. (2014). The carbohydrate-active enzymes database (CAZy) in 2013. Nucleic Acids Res. 2014;42(Database issue):D490-5. DOI:10.1093/nar/gkt1178 | PubMed ID:24270786 [CAZyDB2014]

All Medline abstracts: PubMed

Glycoside Hydrolase Family GH91
Active site residues
CAZy DB link

History of reclassification

Entries in Glycoside Hydrolase Family 91 were reclassified to Polysaccharide Lyase Family 19 on 30 July 2008 due to recommendations of the NC-IUBMB, which stated that these enzymes are lyases, as there is no water involved in the reaction. Indeed, polysaccharide cleavage in some members occurs via intramolecular hydroxide attack, rather than glycosidic bond hydrolysis (see EC and EC

The family was placed back to Glycoside Hydrolase Family 91 on 20 April 2010 due to direct analogy with the lytic transglycosidases of GH23, GH102, GH103, and GH104 and in particular the observation of a hydrolase (di-fructofuranose 1,2':2,3' dianhydride hydrolase, DFA-IIIase) in this family [3, 4].

Substrate specificities

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Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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Family Firsts

First stereochemistry determination
First catalytic nucleophile identification
First general acid/base residue identification
First 3-D structure


  1. H. Sakurai, A. Yokota, Y. Sumita, Y. Mori, H. Matsui and F. Tomita, Metabolism of DFA III by Arthrobacter sp. H65-7: purification and properties of a DFA III hydrolysis enzyme (DFA IIIase). Biosci. Biotechnol. Biochem. 61 (1997), pp. 989–993. DOI: 10.1271/bbb.61.989

  2. Saito K, Sumita Y, Nagasaka Y, Tomita F, and Yokota A. (2003). Molecular cloning of the gene encoding the di-D-Fructofuranose 1,2':2,3' dianhydride hydrolysis enzyme (DFA IIIase) from Arthrobacter sp. H65-7. J Biosci Bioeng. 2003;95(5):538-40. DOI:10.1016/s1389-1723(03)80058-0 | PubMed ID:16233453 [Saito2003]