Auxiliary Activity Family 10

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• Author: ^^^Vincent Eijsink^^^ and ^^^Gustav Vaaje-Kolstad^^^
• Responsible Curator: ^^^Vincent Eijsink^^^

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Auxiliary Activity Family 10
Clan	none, structurally related to AA9
Mechanism	lytic oxidase
Active site residues	mononuclear copper ion
CAZy DB link
https://www.cazy.org/AA10.html

Substrate specificities

So far AA10s have been shown to target chitin and cellulose, but binding has also been demonstrated for chitosan, bacterial surfaces....

Before the proteins belonging to AA10 were identified as enzymes, they were known as chitin binding proteins (CBPs). The reason for this is that most characterized proteins had been identified in chitinolytic systems such as that of Serratia marcescens (REF), several Streptomyces species (REFs), ......, and show no other obvious function than just binding the substrate. Thus there exists several papers that have analyzed the binding preferences of AA10s.

Shortly after CBP21 from S. marcescens was shown to specifically cleave chitin chains [1], CelS2 from Streptomyces coelicolor (also known as ScAA10D) was shown to act specifically on cellulose by a apparently identical monooxygenase activity [2]. In contrast to CBP21, which is a single AA10 module that binds strongly to beta-chitin, CelS2 has a CBM2 attached to the C-terminal side of the AA10 module that specifies binding of the enzyme cellulose.

Please see these references for an essential introduction to the CAZy classification system: [3, 4].

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

In 2005, the structure CBP21 from S. marcescens, was solved and represents the first structure in the AA10 family 2BEM [5]. The CBP21 wild type structure has three molecules in the asymetric unit, which of only chain C show electron density for a metal bound in the metal binding motif (modeled as a sodium ion, but is probably a reduced copper ion with low occupancy). Later the same year the structure of the CBP21-Y54A mutant was solved (different crystal form and space group), showing only one molecule in the asymetric unit and no trace of electron density for a metal ion bound in the active site 2BEN [6]. In 2012 the solution structure of CBP21 wild type (apo-form) was solved by NMR 2LHS [7].

EfCBM33A from Enterococcus faecalis

Family Firsts

First stereochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

CBP21, the single AA10-type LPMO from the Gram negative bacterium Serratia marcescens. Entry in the protein data bank: [1]

References

1. Vaaje-Kolstad G, Westereng B, Horn SJ, Liu Z, Zhai H, Sørlie M, and Eijsink VG. (2010). An oxidative enzyme boosting the enzymatic conversion of recalcitrant polysaccharides. Science. 2010;330(6001):219-22. DOI:10.1126/science.1192231 |
2. Forsberg Z, Vaaje-Kolstad G, Westereng B, Bunæs AC, Stenstrøm Y, MacKenzie A, Sørlie M, Horn SJ, and Eijsink VG. (2011). Cleavage of cellulose by a CBM33 protein. Protein Sci. 2011;20(9):1479-83. DOI:10.1002/pro.689 |

3. Davies, G.J. and Sinnott, M.L. (2008) Sorting the diverse: the sequence-based classifications of carbohydrate-active enzymes. Biochem. J. (BJ Classic Paper, online only). DOI: 10.1042/BJ20080382

4. Cantarel BL, Coutinho PM, Rancurel C, Bernard T, Lombard V, and Henrissat B. (2009). The Carbohydrate-Active EnZymes database (CAZy): an expert resource for Glycogenomics. Nucleic Acids Res. 2009;37(Database issue):D233-8. DOI:10.1093/nar/gkn663 |
5. Vaaje-Kolstad G, Houston DR, Riemen AH, Eijsink VG, and van Aalten DM. (2005). Crystal structure and binding properties of the Serratia marcescens chitin-binding protein CBP21. J Biol Chem. 2005;280(12):11313-9. DOI:10.1074/jbc.M407175200 |
6. Vaaje-Kolstad G, Horn SJ, van Aalten DM, Synstad B, and Eijsink VG. (2005). The non-catalytic chitin-binding protein CBP21 from Serratia marcescens is essential for chitin degradation. J Biol Chem. 2005;280(31):28492-7. DOI:10.1074/jbc.M504468200 |
7. Aachmann FL, Sørlie M, Skjåk-Bræk G, Eijsink VG, and Vaaje-Kolstad G. (2012). NMR structure of a lytic polysaccharide monooxygenase provides insight into copper binding, protein dynamics, and substrate interactions. Proc Natl Acad Sci U S A. 2012;109(46):18779-84. DOI:10.1073/pnas.1208822109 |