Polysaccharide Lyase Family 7

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• Authors: ^^^Nadine Gerlach^^^ and ^^^Jan-Hendrik Hehemann^^^
• Responsible Curator: ^^^Jan-Hendrik Hehemann^^^

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Polysaccharide Lyase Family PL7
3D Structure	β jelly roll
Mechanism	β-elimination
Active site residues	known
CAZy DB link
https://www.cazy.org/PL7.html

Mechanism

Alginate lyases (Alys) of all families, PL5-7, PL14, PL15, PL17-18, cleave the glycosidic bond via β-elimination. Most PL7s are endo-active, i.e. acting within a poly- or oligosaccharide and releasing smaller alginate fragments.

exo activity [1]

Kinetics and catalytic residues

Arg, Gln, His, Tyr form active site [2]

His removes negative charge of the substrate

Substrate specificities

The polysaccharide lyase family 7 (PL7) contains 5 subfamilies [3]. All characterized PL7 enzymes were alginate lyases specific for the anionic, gel forming polysaccharide alginate. The substrate specificity depends on the source of alginate, i.e. derived from brown seaweed or mucoid bacteria Pseudomonas spp. and Azotobacter vinelandii, as well as geographical and saisonal parameters. Alginate is an heteropolysaccharide, consisting of β-D-mannuronate (M) and α-L-guluronate (G). These monosaccharides can occur in homogenous and heterogenous blocks. Hence, PL7 lyases can be mannuronate (EC 4.2.2.3), guluronate (EC 4.2.2.11) or mixed link (EC 4.2.2.-) specific. Despite the pefernce for M- or G-enriched blocks, most PL7s also have a moderate to low processivity for the other building block.

Substitution of hydrophobic amino acids in the isoleucine site of domain QIH could have an enormous influence on the high-affinity to pM or pG. This isoleucine was reconfirmed to be indispensable for recognition of the pG or G-G bond [4]

Three-dimensional structures

Figure 2. 3D Structure of endo- and exo-active PL7s [1]. (A,C) AlyA1 and (B, D) AlyA5 from Zobellia galaactinovorans DsijT shown as cartoon (A,C) and surface structure (B,D) with superimposed tetrasaccharide from PDB:2ZAA [5]

PL 7 is a very well biochemical characterized family with almost 40 entries in the CAZy data base [6]. Structural insights on the other hand are still restricted with nine 3D structures from only eight bacterial strains (status at CAZy in August 2019). The first structure of a PL7 was determined from Pseudomonas aeruginosa by multiple isomorphous replacement (MIR) at 2.0 Å resolution [7]. Just like PL14, PL7 belongs to the jelly roll family with a wide open cleft harboring the active site.

endo vs. exo [1]

Evolution of Aly PULs

[8]

Family Firsts

First catalytic endo-activity

First catalytic exo-activity

AlyA5 from Zobellia galactanivorans DsijT [1]

First 3-D apo-structure

PA1167 from Pseudomonas aeruginosa [7]

First 3-D holo-structure

A1-II from Sphingomons sp. A1 [5]

References

1. Thomas F, Lundqvist LC, Jam M, Jeudy A, Barbeyron T, Sandström C, Michel G, and Czjzek M. (2013). Comparative characterization of two marine alginate lyases from Zobellia galactanivorans reveals distinct modes of action and exquisite adaptation to their natural substrate. J Biol Chem. 2013;288(32):23021-37. DOI:10.1074/jbc.M113.467217 |
2. Yamasaki M, Ogura K, Hashimoto W, Mikami B, and Murata K. (2005). A structural basis for depolymerization of alginate by polysaccharide lyase family-7. J Mol Biol. 2005;352(1):11-21. DOI:10.1016/j.jmb.2005.06.075 |
3. Lombard V, Bernard T, Rancurel C, Brumer H, Coutinho PM, and Henrissat B. (2010). A hierarchical classification of polysaccharide lyases for glycogenomics. Biochem J. 2010;432(3):437-44. DOI:10.1042/BJ20101185 |
4. Deng S, Ye J, Xu Q, and Zhang H. (2014). Structural and functional studies on three alginate lyases from Vibrio alginolyticus. Protein Pept Lett. 2014;21(2):179-87. DOI:10.2174/09298665113206660094 |

5. Crystal Structure of Family 7 Alginate Lyase A1-II' H191N/Y284F in Complex with Substrate (GGMG)

6. Lombard V, Golaconda Ramulu H, Drula E, Coutinho PM, and Henrissat B. (2014). The carbohydrate-active enzymes database (CAZy) in 2013. Nucleic Acids Res. 2014;42(Database issue):D490-5. DOI:10.1093/nar/gkt1178 |
7. Yamasaki M, Moriwaki S, Miyake O, Hashimoto W, Murata K, and Mikami B. (2004). Structure and function of a hypothetical Pseudomonas aeruginosa protein PA1167 classified into family PL-7: a novel alginate lyase with a beta-sandwich fold. J Biol Chem. 2004;279(30):31863-72. DOI:10.1074/jbc.M402466200 |
8. Hehemann JH, Correc G, Barbeyron T, Helbert W, Czjzek M, and Michel G. (2010). Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature. 2010;464(7290):908-12. DOI:10.1038/nature08937 |