Polysaccharide Lyase family classification

Introduction

Polysaccharide Lyases (EC 4.2.2.-) are a group of enzymes that cleave uronic acid-containing polysaccharide chains via a β-elimination mechanism to generate an unsaturated hexenuronic acid residue and a new reducing end. This section of the CAZy database presents a classification of these enzymes in families and subfamilies based on amino acid sequence similarities, intended to reflect their structural features [1].

These enzymes show a large variety of fold types (or classes) [1] [2], suggesting that PLs have been invented more than once during evolution from totally different scaffolds.

Just as for the glycoside hydrolases and the glycosyltransferases, the sequence-based families of polysaccharide lyases are frequently polyspecific (i.e. contain enzymes acting on different substrates or that generate different products). Grouping into mostly monospecific subfamilies described in [1] provides an effort to palliate this polyspecificity. Subfamily information is provided throughout the ensemble of the polysaccharide lyase families described so far.

Catalytic Mechanism

For the purpose of this family classification, the scope of the term PL is restricted to those enzymes which operate according to the general syn- and anti-elimination mechanisms described in [1], to produce a terminal hexenuronic acid moiety by β-elimination. This constitutes a clear distinction from the broader IUBMB classification of carbon-oxygen lyases acting on polysaccharides under EC 4.2.2.-, where other enzyme mechanisms have been described. Several of the lyases non-included in this classification present mechanistic commonality with glycoside hydrolases and have therefore been included among these families.

Tables for Direct Access

- PL Family Number

12345678910111213141516171819202122232425262728293031323334353637383940
414243
Non-Classified Sequences

- PL SubFamily Number

PL112345678910111213
PL212
PL312345
PL412345
PL6123
PL712345
PL81234
PL91234
PL10123
PL1112
PL12123
PL1412345
PL1512
PL1712
PL2212

- PL Classification Statistics

Modules in present families 62980
Non-Classified modules 2758

Notes

[1Lombard V, Bernard T, Rancurel C, Brumer H, Coutinho PM, Henrissat B (2010) A hierarchical classification of polysaccharide lyases for glycogenomics. Biochem. J. 432:437-444 [PMID : 20925655].

[2Garron ML, Cygler M (2010) Structural and mechanistic classification of uronic acid-containing polysaccharide lyases Glycobiology, 20:1547-73 [PMID : 20805221].

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