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Glycoside Hydrolase Family 121

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Glycoside Hydrolase Family GH121
Clan none
Mechanism retaining
Active site residues not known
CAZy DB link

Substrate specificities

This family of glycoside hydrolases contains β-L-arabinobiosidases, as demonstrated for HypBA2 from Bifidobacterium longum JCM 1217 [1]. HypBA2 liberates the disaccharide Arafβ1-2Araf (β-Ara2, a substrate of the GH127 β-L-arabinofuranosidase from B. longum JCM 1217 [2]) from unmodified Arafβ1-2Arafβ1-2Arafβ-hydroxyproline (Ara3-Hyp), but not Arafα1-3Arafβ1-2Arafβ1-2Arafβ-Hyp (Ara4-Hyp) or Arafβ1-2Arafβ-Hyp (Ara2-Hyp). HypBA2 directly liberates β-Ara2 from hydroxyproline-rich glycoproteins (HRGPs) such as carrot extensin and potato lectin. The family members are only found from prokaryote genomes, such as bacteria and actinomycetes.

Kinetics and Mechanism

HypBA2 is a retaining enzyme. The stereochemical course of the reaction was shown by transglycosylation activity toward 1-alkanols, such as methanol; the resulting Arafβ1-2Arafβ-Me was identified by 1H-NMR and 13C-NMR analysis.

Catalytic Residues

Not known.

Three-dimensional structures

Not known.

Family Firsts

First stereochemistry determination
Shown to be retaining for HypBA2 enzyme by measurement of glycosyl transfer reactions to methanol and the 1H-NMR and 13C-NMR spectra [1].
First catalytic nucleophile identification
No experimental proof.
First general acid/base residue identification
No experimental proof.
First 3-D structure
Not known.


  1. Fujita K, Sakamoto S, Ono Y, Wakao M, Suda Y, Kitahara K, and Suganuma T. (2011) Molecular cloning and characterization of a beta-L-Arabinobiosidase in Bifidobacterium longum that belongs to a novel glycoside hydrolase family. J Biol Chem. 286, 5143-50. DOI:10.1074/jbc.M110.190512 | PubMed ID:21149454 | HubMed [Fujita2011A]
  2. Fujita K, Takashi Y, Obuchi E, Kitahara K, and Suganuma T. (2011) Characterization of a novel β-L-Arabinofuranosidase in Bifidobacterium longum: functional elucidation of A DUF1680 family member. J Biol Chem. 286, 38079-85. DOI:10.1074/jbc.M111.248690 | PubMed ID:21914802 | HubMed [Fujita2011B]
All Medline abstracts: PubMed | HubMed