[[Image:EndovsexoPL7_Thomas_et_al_2013.jpg|thumb|400px|'''Figure 2.''' 3D Structure of endo- and exo-active PL7s (A,C) AlyA1 and (B, D) AlyA5 from ''Zobellia galaactinovorans'' DsijT. ]]
[[Image:EndovsexoPL7_Thomas_et_al_2013.jpg|thumb|400px|'''Figure 2.''' 3D Structure of endo- and exo-active PL7s (A,C) AlyA1 and (B, D) AlyA5 from ''Zobellia galaactinovorans'' DsijT. ]]
PL 7 is a very well biochemical characterized family with almost 40 entries in the CAZy data base <cite>Lombard2014</cite>. Structural insights on the other hand are still restricted with nine 3D structures from only eight bacterial strains (status at CAZy.org in August 2019). The first structure of a PL7 was determined from''Pseudomonas aeruginosa'' by multiple isomorphpus replacement(MIR) at 2.0 Å resolution <cite>Yamasaki2004</cite>. Just like PL14, PL7 belongs to the jelly roll family with a wide open cleft harboring the active site.
PL 7 is a very well biochemical characterized family with almost 40 entries in the CAZy data base <cite>Lombard2014</cite>. Structural insights on the other hand are still restricted with nine 3D structures from only eight bacterial strains (status at [http://www.cazy.org/PL7.html CAZy] in August 2019). The first structure of a PL7 was determined from ''Pseudomonas aeruginosa'' by multiple isomorphpus replacement(MIR) at 2.0 Å resolution <cite>Yamasaki2004</cite>. Just like PL14, PL7 belongs to the jelly roll family with a wide open cleft harboring the active site.
endo vs. exo <cite>Thomas2013</cite>
endo vs. exo <cite>Thomas2013</cite>
Revision as of 05:34, 1 August 2019
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Authors: ^^^Nadine Gerlach^^^ and ^^^Jan-Hendrik Hehemann^^^
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.
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 (A,C) AlyA1 and (B, D) AlyA5 from Zobellia galaactinovorans DsijT.
PL 7 is a very well biochemical characterized family with almost 40 entries in the CAZy data base [5]. 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 isomorphpus replacement(MIR) at 2.0 Å resolution [6]. Just like PL14, PL7 belongs to the jelly roll family with a wide open cleft harboring the active site.
