Glycoside Hydrolase Family 143

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• Author: Grete Raba
• Responsible Curator: Ana Luis

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Glycoside Hydrolase Family GH143
Clan	GH-x
Mechanism	retaining (inferred)
Active site residues	known
CAZy DB link
https://www.cazy.org/GH143.html

Substrate specificities

The members of GH142 family are 1-keto-3-deoxy-D-lyxo-heptulosaric acid (DHA) hydrolases (EC 3.2.1.-). The first characterized enzyme from this family was the N-terminus of BT1020 from Bacteroides thetaiotaomicron [1]. BT1020 cleaves the D-DHA- β-2,3-D-GalA linkage in rhamnogalacturonan II (RG II) in pectin.

Kinetics and Mechanism

The structural similarities between BT1020 N-terminus from GH143 and sialidases from GH33 suggest a retaining catalytic mechanism [1]. Understanding specific kinetics and mechanisms of GH143 enzymes needs further studies.

Catalytic Residues

The active site of DHA-hydrolase (N-terminus of BT1020) contains tyrosine and glutamate residues that function as the catalytic nucleophile and acid-base residues [1].

Three-dimensional structures

The N-terminus of BT1020 is made of 380 amino acid residues, arranged into 5-bladed β-propeller structure with 2-keto-3-deoxy-D-lyxo-heptulosaric acid (DHA)-hydrolase activity [1].

Family Firsts

First stereochemistry determination

Not yet identified.

First catalytic nucleophile identification

BT1020 from Bacteroides thetaiotaomicron [1].

First general acid/base residue identification

BT1020 from Bacteroides thetaiotaomicron [1].

First 3-D structure

BT1020 from Bacteroides thetaiotaomicron [1].

References

1. Ndeh D, Rogowski A, Cartmell A, Luis AS, Baslé A, Gray J, Venditto I, Briggs J, Zhang X, Labourel A, Terrapon N, Buffetto F, Nepogodiev S, Xiao Y, Field RA, Zhu Y, O'Neil MA, Urbanowicz BR, York WS, Davies GJ, Abbott DW, Ralet MC, Martens EC, Henrissat B, and Gilbert HJ. Complex pectin metabolism by gut bacteria reveals novel catalytic functions. Nature. 2017 Apr 6;544(7648):65-70. DOI:10.1038/nature21725 |