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Glycoside Hydrolase Family 143

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Glycoside Hydrolase Family GH143
Clan GH-x
Mechanism retaining (inferred)
Active site residues known
CAZy DB link

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].


  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. (2017). Complex pectin metabolism by gut bacteria reveals novel catalytic functions. Nature. 2017;544(7648):65-70. DOI:10.1038/nature21725 | PubMed ID:28329766 [Ndeh2017]