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Difference between revisions of "Glycoside Hydrolase Family 129"
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== Substrate specificities == | == Substrate specificities == | ||
This family of glycoside hydrolases was recently established for NagBb from | This family of glycoside hydrolases was recently established for NagBb from | ||
| − | ''Bifidobacterium bifidum'' JCM 1254, which shows slight sequence similarity with [[ | + | ''Bifidobacterium bifidum'' JCM 1254, which shows slight sequence similarity with [[GH101]] endo-α-''N''-acetylgalactosaminidases <cite>Kiyohara2012a</cite>. NagBb more rapidly act on GalNAcα1-''p''NP than Galβ1-3GalNAcα1-''p''NP; therefore its substrate specificity is quite different from [[GH101]] enzymes (EC [{{EClink}}3.2.1.97 3.2.1.97]). It is also different from those of previously known exo-α-''N''-acetylgalactosaminidases (EC [{{EClink}}3.2.1.49 3.2.1.49]) in [[GH27]], [[GH36]] and [[GH109]]. Thus, NagBb should be called as exo/endo-α-''N''-acetylgalactosaminidase. NagBb most preferably hydrolyzes GalNAcα1-Ser, a minimal structure of Tn antigen on mucin-type glycoproteins, suggesting that NagBb might be involved in degradation of intestinal mucins. The members of GH129 are distributed in several bifidobacterial species such as ''B. longum'' subsp. ''longum'', ''B. longum'' subsp. ''infants'' and ''B. breve'', which are frequently found in intestines of infants. |
== Kinetics and Mechanism == | == Kinetics and Mechanism == | ||
| − | NagBb is a retaining enzyme. The stereochemistry of hydrolysis has been monitored by normal-phase HPLC using GalNAcα1-''p''NP as a substrate. GH129 is distantly related with [[ | + | NagBb is a retaining enzyme. The stereochemistry of hydrolysis has been monitored by normal-phase HPLC using GalNAcα1-''p''NP as a substrate. GH129 is distantly related with [[GH101]] as well as [[GH13]] α-amylases; the latter two family members are also classified as retaining enzymes. |
== Catalytic Residues == | == Catalytic Residues == | ||
| − | Asp-435 in NagBb is predicted as catalytic nucleophile by the remote homology-based fold recognition method using [[ | + | Asp-435 in NagBb is predicted as catalytic nucleophile by the remote homology-based fold recognition method using [[GH13]] α-amylase 1 (TVAI) from ''Thermoactinomyces vulgaris'' R-47 (PDB code [{{PDBlink}}1JI1 1JI1]) as a template. Asp-330 in NagBb may be "fixer", the third invariant catalytic residue conserved in [[GH101]] and [[GH13]] enzymes. General acid/base residue is unknown. |
== Three-dimensional structures == | == Three-dimensional structures == | ||
Revision as of 03:32, 8 March 2012
This page is currently under construction. This means that the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information should be considered to be under revision and may be subject to major changes.
- Author: ^^^Hisashi Ashida^^^
- Responsible Curator: ^^^Shinya Fushinobu^^^
| Glycoside Hydrolase Family GH129 | |
| Clan | GH-x |
| Mechanism | retaining |
| Active site residues | Asp |
| CAZy DB link | |
| https://www.cazy.org/GH129.html | |
Substrate specificities
This family of glycoside hydrolases was recently established for NagBb from Bifidobacterium bifidum JCM 1254, which shows slight sequence similarity with GH101 endo-α-N-acetylgalactosaminidases [1]. NagBb more rapidly act on GalNAcα1-pNP than Galβ1-3GalNAcα1-pNP; therefore its substrate specificity is quite different from GH101 enzymes (EC 3.2.1.97). It is also different from those of previously known exo-α-N-acetylgalactosaminidases (EC 3.2.1.49) in GH27, GH36 and GH109. Thus, NagBb should be called as exo/endo-α-N-acetylgalactosaminidase. NagBb most preferably hydrolyzes GalNAcα1-Ser, a minimal structure of Tn antigen on mucin-type glycoproteins, suggesting that NagBb might be involved in degradation of intestinal mucins. The members of GH129 are distributed in several bifidobacterial species such as B. longum subsp. longum, B. longum subsp. infants and B. breve, which are frequently found in intestines of infants.
Kinetics and Mechanism
NagBb is a retaining enzyme. The stereochemistry of hydrolysis has been monitored by normal-phase HPLC using GalNAcα1-pNP as a substrate. GH129 is distantly related with GH101 as well as GH13 α-amylases; the latter two family members are also classified as retaining enzymes.
Catalytic Residues
Asp-435 in NagBb is predicted as catalytic nucleophile by the remote homology-based fold recognition method using GH13 α-amylase 1 (TVAI) from Thermoactinomyces vulgaris R-47 (PDB code 1JI1) as a template. Asp-330 in NagBb may be "fixer", the third invariant catalytic residue conserved in GH101 and GH13 enzymes. General acid/base residue is unknown.
Three-dimensional structures
Family Firsts
- First stereochemistry determination
- NagBb from Bifidobacterium bifidum JCM 1254 by normal-phase HPLC
- First catalytic nucleophile identification
- First general acid/base residue identification
- First 3-D structure
References
-
Kiyohara M, Nakatomi T, Kurihara S, Fushinobu S, Suzuki H, Tanaka T, Shoda S, Kitaoka M, Katayama T, Yamamoto K, Ashida H. α-N-acetylgalactosaminidase from infant-associated bifidobacteria belonging to novel glycoside hydrolase family 129 is implicated in alternative mucin degradation pathway. J Biol Chem. 2012 Jan 2;287(1):693-700.
Note: Due to a problem with PubMed data, this reference is not automatically formatted. Please see these links out: DOI:10.1074/jbc.M111.277384 PMID: 22090027