Family 6 Carbohydrate Binding Modules in β-Agarases Display Exquisite Selectivity for the Non-reducing Termini of Agarose Chains

Carbohydrate recognition is central to the biological and industrial exploitation of plant structural polysaccharides. These insoluble polymers are recalcitrant to microbial degradation, and enzymes that catalyze this process generally contain non-catalytic carbohydrate binding modules (CBMs) that potentiate activity by increasing substrate binding. Agarose, a repeat of the disaccharide 3,6-anhydro-α-l-galactose-(1,3)-β-d-galactopyranose-(1,4), is the dominant matrix polysaccharide in marine algae, yet the role of CBMs in the hydrolysis of this important polymer has not previously been explored. Here we show that family 6 CBMs, present in two different β-agarases, bind specifically to the non-reducing end of agarose chains, recognizing only the first repeat of the disaccharide. The crystal structure of one of these modules Aga16B-CBM6-2, in complex with neoagarohexaose, reveals the mechanism by which the protein displays exquisite specificity, targeting the equatorial O4 and the axial O3 of the anhydro-l-galactose. Targeting of the CBM6 to the non-reducing end of agarose chains may direct the appended catalytic modules to areas of the plant cell wall attacked by β-agarases where the matrix polysaccharide is likely to be more amenable to further enzymic hydrolysis. Carbohydrate recognition is central to the biological and industrial exploitation of plant structural polysaccharides. These insoluble polymers are recalcitrant to microbial degradation, and enzymes that catalyze this process generally contain non-catalytic carbohydrate binding modules (CBMs) that potentiate activity by increasing substrate binding. Agarose, a repeat of the disaccharide 3,6-anhydro-α-l-galactose-(1,3)-β-d-galactopyranose-(1,4), is the dominant matrix polysaccharide in marine algae, yet the role of CBMs in the hydrolysis of this important polymer has not previously been explored. Here we show that family 6 CBMs, present in two different β-agarases, bind specifically to the non-reducing end of agarose chains, recognizing only the first repeat of the disaccharide. The crystal structure of one of these modules Aga16B-CBM6-2, in complex with neoagarohexaose, reveals the mechanism by which the protein displays exquisite specificity, targeting the equatorial O4 and the axial O3 of the anhydro-l-galactose. Targeting of the CBM6 to the non-reducing end of agarose chains may direct the appended catalytic modules to areas of the plant cell wall attacked by β-agarases where the matrix polysaccharide is likely to be more amenable to further enzymic hydrolysis. The polysaccharides in the cell wall of both marine and terrestrial plants represent the most abundant reservoir of organic carbon in the biosphere. The microbial hydrolysis of these polymers is not only central to the carbon cycle but also of considerable industrial significance. Indeed, the enzymes that catalyze this process are already widely used in the paper/pulp, animal feed, fruit juice, detergent, and textile sectors (1Subramaniyan S. Prema P. Crit. Rev. Biotechnol. 2002; 22: 33-64Crossref PubMed Scopus (524) Google Scholar, 2Warren R.A. Annu. Rev. Microbiol. 1996; 50: 183-212Crossref PubMed Scopus (292) Google Scholar, 3Hazlewood G.P. Gilbert H.J. Prog. Nucleic Acids Res. Mol. Biol. 1998; 61: 211-241Crossref PubMed Google Scholar). The major potential industrial application for these enzymes is, however, the conversion of the energy stored in plant structural polysaccharides, estimated to be equivalent to 600 billion barrels of oil, into bioethanol, a renewable and environmentally friendly fuel (4Boudet A.M. Kajita S. Grima-Pettenati J. Goffner D. Trends Plant. Sci. 2003; 8: 576-581Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar). The complex interactions between the polysaccharides within the plant cell wall restrict their accessibility to enzyme attack. To overcome this problem glycoside hydrolases that degrade the plant cell wall often have a complex molecular architecture comprising both catalytic domains and non-catalytic carbohydrate binding modules (CBMs) 3The abbreviations used are: CBM, carbohydrate binding module; GH, glycoside hydrolase; SeMet, selenomethionine. (5Boraston A.B. Bolam D.N. Gilbert H.J. Davies G.J. Biochem. J. 2004; 382: 769-781Crossref PubMed Scopus (1537) Google Scholar). By binding to plant structural polysaccharides, CBMs bring the appended catalytic domain into intimate contact with its target substrate and potentiate catalysis (6Tomme P. Van Tilbeurgh H. Pettersson G. Van Damme J. Vandekerckhove J. Knowles J. Teeri T. Claeyssens M. Eur. J. Biochem. 1988; 170: 575-581Crossref PubMed Scopus (490) Google Scholar, 7Maglione G. Matsushita O. Russell J.B. Wilson D.B. Appl. Environ. Microbiol. 1992; 58: 3593-3597Crossref PubMed Google Scholar, 8Boraston A.B. Kwan E. Chiu P. Warren R.A. Kilburn D.G. J. Biol. Chem. 2003; 278: 6120-6127Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar, 9Gill J. Rixon J.E. Bolam D.N. McQueen-Mason S. Simpson P.J. Williamson M.P. Hazlewood G.P. Gilbert H.J. Biochem. J. 1999; 342: 473-480Crossref PubMed Scopus (69) Google Scholar, 10Bolam D.N. Ciruela A. McQueen-Mason S. Simpson P. Williamson M.P. Rixon J.E. Boraston A. Hazlewood G.P. Gilbert H.J. Biochem. J. 1998; 331: 775-781Crossref PubMed Scopus (239) Google Scholar). A recent study also showed that a CBM, which is not appended to a catalytic module, is able to increase substrate access by disrupting the crystalline structure of the polysaccharide chitin (11Vaaje-Kolstad G. Horn S.J. van Aalten D.M. Synstad B. Eijsink V.G. J. Biol. Chem. 2005; 280: 28492-28497Abstract Full Text Full Text PDF PubMed Scopus (307) Google Scholar). CBMs are currently grouped into 45 sequence-based families (5Boraston A.B. Bolam D.N. Gilbert H.J. Davies G.J. Biochem. J. 2004; 382: 769-781Crossref PubMed Scopus (1537) Google Scholar, 12Coutinho P.M. Henrissat B. Recent Advances in Carbohydrate Bioengineering. 1999; (Royal Society of Chemistry, Cambridge): 3-12Google Scholar), analogous to the classification of the catalytic modules of these enzymes into glycoside hydrolase families (GHs) (13Henrissat B. Teeri T.T. Warren R.A. FEBS Lett. 1998; 425: 352-354Crossref PubMed Scopus (256) Google Scholar) (available at afmb.cnrsmrs.fr/CAZY). CBM families, such as 1, 2a, 3a, 5, and 10, contain “type A” modules, which bind to crystalline polysaccharides. The ligand specificity of the different members of these families is highly conserved (9Gill J. Rixon J.E. Bolam D.N. McQueen-Mason S. Simpson P.J. Williamson M.P. Hazlewood G.P. Gilbert H.J. Biochem. J. 1999; 342: 473-480Crossref PubMed Scopus (69) Google Scholar, 14Hogg D. Pell G. Dupree P. Goubet F. Martin-Orue S.M. Armand S. Gilbert H.J. Biochem. J. 2003; 371: 1027-1043Crossref PubMed Google Scholar) even though they are present in distinct glycoside hydrolases such as cellulases, xylanases, mannanases, xylan acetyl esterases, and arabinofuranosidases (14Hogg D. Pell G. Dupree P. Goubet F. Martin-Orue S.M. Armand S. Gilbert H.J. Biochem. J. 2003; 371: 1027-1043Crossref PubMed Google Scholar, 15Ferreira L.M. Wood T.M. Williamson G. Faulds C. Hazlewood G.P. Black G.W. Gilbert H.J. Biochem. J. 1993; 294: 349-355Crossref PubMed Scopus (140) Google Scholar, 16Kellett L.E. Poole D.M. Ferreira L.M. Durrant A.J. Hazlewood G.P. Gilbert H.J. Biochem. J. 1990; 272: 369-376Crossref PubMed Scopus (149) Google Scholar). By contrast, type B and type C CBMs, where the with chains at the generally polysaccharides that are by the appended catalytic A.B. D. Kilburn D.G. Davies G.J. J. Mol. Biol. 2002; PubMed Scopus Google Scholar, M. E. E. S. Simpson P.J. Gilbert H.J. Williamson M.P. O. Biochem. J. PubMed Scopus Google Scholar). specificity in type B and C CBM families is highly for CBM family that bind to xylan and A.B. D. Kilburn D.G. Davies G.J. J. Mol. Biol. 2002; PubMed Scopus Google Scholar, M. E. E. S. Simpson P.J. Gilbert H.J. Williamson M.P. O. Biochem. J. PubMed Scopus Google Scholar). CBM6 one of the most families with members present in enzymes that a of different Bolam D.N. M. Henrissat B. Ferreira L.M. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, C. Gilbert H.J. Boraston A.B. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). the crystal structure of CBM6 modules in a and two and have been Bolam D.N. M. Henrissat B. Ferreira L.M. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, C. Gilbert H.J. Boraston A.B. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar, Bolam D.N. Ferreira L.M. Henrissat B. A. Gilbert H.J. M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, A.B. Warren R.A. Kilburn D.G. Davies G. J. Mol. Biol. 2003; PubMed Scopus Google Scholar). The a which is to CBM two one of which a the ligand to the in the of CBM families with this the of recognition in different members of the and the ligand binding is within the the two M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, C. Gilbert H.J. Boraston A.B. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar), By contrast, the of to of chains and the non-reducing of xylan and are within the that A Bolam D.N. M. Henrissat B. Ferreira L.M. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, Bolam D.N. Ferreira L.M. Henrissat B. A. Gilbert H.J. M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). not only the ligand binding in but the family “type and binding displays both type B and type C ligand binding is important marine polysaccharide of molecular 2002; 50: Scopus Google Scholar), the J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The polysaccharide a which is highly recalcitrant to enzyme S. A. J. Mol. Biol. PubMed Scopus Google Scholar). The agarose is by and β-agarases, which the and J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). The of in the are only enzymes in glycoside hydrolase family in the that are as The mechanism by which these enzymes are able to access agarose chains is currently the recent of the crystal structure of a reveals agarose binding in the catalytic that may to of the structure J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). are in β-agarases, their is Here we show that family 6 CBMs in two β-agarases, and they contain catalytic modules to glycoside hydrolase families and bind to the non-reducing end of agarose The crystal structure of one of these CBMs in complex with reveals a of between ligand and the exploitation of the that are to the of agarose as recognition to the exquisite specificity by these protein modules for the marine The of the binding of these is and the and family 6 CBMs by and the and the in The into and to and the CBM6 modules of into and to and The which contain a in the at to to a of and the for a further at The and to and insoluble The in the insoluble in and 6 and by The protein the by the matrix with a of 6 to in A. The protein a to in A. To the E. as in A. Bolam D.N. Gilbert H.J. Ferreira L.M. A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar), and the protein the for the in molecular and in the the of CBM6 of the to the as the and the in To the of the the To in the crystal structure of the and the CBM6 not contain These in and we used the to the crystal structure of the of and and by the with as previously D. M. Davies G.J. Gilbert H.J. Sci. S. A. 2005; PubMed Scopus Google Scholar). binding of the CBM6 to polysaccharides by as previously Bolam D.N. P. Hazlewood G.P. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (69) Google Scholar). To the polysaccharide by and to the to binding also by at Bolam D.N. M. Henrissat B. Ferreira L.M. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar) a and the ligand in the to of a the protein at in a cell at with a by of ligand at for of by a binding The the and the of binding the To the role of in ligand binding the with and of of both the protein and the by the with a of and to with The protein used at of and with of neoagarohexaose, and of protein and of The which at in with by in with in of with and in the and in the at The with a to with the with the Biol. 1999; PubMed Scopus Google Scholar). A of the as and used to 1992; PubMed Scopus Google Scholar). are in and structure of into the of the to for and structure into the of the to for and structure into the of the to for and structure into the of the to for and structure into the of the to for and structure B B substrate B B The into the of the to for and structure in a of the with in and in at at the a The for a with of and Recent to the for and 1992; and protein Scholar) and in the Biol. 50: PubMed Scopus Google Scholar) of the for of are in and structure of the and in G. T. PubMed Scopus Google Scholar). for into with with by of and with P. Biol. 2004; PubMed Scopus Google Scholar) and Biol. PubMed Scopus Google Scholar), but used as a for and the A. Biol. 1999; PubMed Scopus Google Scholar) and to of the and are in of β-agarases and S. are enzymes a and catalytic appended to and two To the of these CBMs, to these modules in E. of these CBMs be as insoluble these be by of and to by of of the to bind to polysaccharides by The of the modules in the of and agarose not its to bind not that in the of further of binding by are in and the is in not these the modules to and neoagarohexaose, which one two and of the disaccharide of and not with the The of the for of the CBMs with a of The that of the CBMs a ligand binding binding the in a The of ligand binding by the modules is of the of CBMs with and the for this in and increase in have been previously A.B. Boraston D. Davies G.J. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, A.B. Biochem. J. 2005; PubMed Scopus Google Scholar, H. Bolam D.N. T. A. Simpson P.J. Williamson M.P. Gilbert H.J. PubMed Scopus Google Scholar, E. E. Kilburn D.G. Sci. S. A. 1996; PubMed Scopus (149) Google of to as by in in the in which the binding in in the in which the binding in a The that with a of of 6 the for the that these protein modules contain two The of binding to and that binding only both are The of binding to agarose as by which is able to as as Bolam D.N. P. Hazlewood G.P. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (69) Google Scholar), is at with the binding to the disaccharide to agarose be by the of disaccharide in this polysaccharide are by the this not the that the which are in a polymer with a of may be the recognition for these to and the end to the that the end is not a recognition The crystal structure of in complex with that at this CBM is for at the non-reducing end of agarose of of CBM6 in the of and but not in the of The to the with cell of a and and in the comprising two one and The have been at the are in displays a of two and and and is a of 6 and The and are at of with the in The in both are The to is highly and has only been in one of the in the The of is to CBM6 is by a C. J. Mol. Biol. 1993; PubMed Scopus Google Scholar), which that the protein displays structural to two family 6 CBMs, by a and The and are and to this is a structural which in A.B. Warren R.A. Kilburn D.G. Davies G. J. Mol. Biol. 2003; PubMed Scopus Google Scholar), Bolam D.N. Ferreira L.M. Henrissat B. A. Gilbert H.J. M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar), and M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) is to be a in to be a C. Gilbert H.J. Boraston A.B. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). is equivalent to the structural in members of the of CBMs, and A.B. D. Kilburn D.G. Davies G.J. J. Mol. Biol. 2002; PubMed Scopus Google Scholar, S.J. Bolam D.N. Gilbert H.J. Ferreira L.M. Davies G.J. PubMed Scopus Google Scholar, P.J. S.J. M. Gilbert H.J. O. Williamson M.P. 2002; PubMed Scopus Google Scholar), where to M. Simpson P.J. S. P. Williamson M.P. S.J. Gilbert H.J. Bolam D.N. O. 2002; PubMed Scopus Google Scholar). the and of the of this with a has a with the and of a with of the of and a be as a structural the and of for a to of the in the The CBM with the non-reducing disaccharide repeat of neoagarohexaose, with the in The with a the of is to the of to A J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar) and the structure of in R.A. J. Mol. Google Scholar). The with the protein between the that the two by to to 5, and to which has been A in family 6 CBMs M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the of CBM families that a the that a B in M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and equivalent to in the target ligand A.B. D. Kilburn D.G. Davies G.J. J. Mol. Biol. 2002; PubMed Scopus Google Scholar, A. Bolam D.N. Gilbert H.J. Ferreira L.M. A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, S.J. Bolam D.N. Gilbert H.J. Ferreira L.M. Davies G.J. PubMed Scopus Google Scholar, P.J. S.J. M. Gilbert H.J. O. Williamson M.P. 2002; PubMed Scopus Google Scholar). By the ligand binding in different members of family 6 CBMs two and a bind to their in to of in also with and in A Bolam D.N. M. Henrissat B. Ferreira L.M. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, Bolam D.N. Ferreira L.M. Henrissat B. A. Gilbert H.J. M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). is to that the first disaccharide repeat of the with A the ligand also B in in the crystal The that the displays the for as the the of binding is one and the of the A carbohydrate recognition that the with B is a also with and this ligand only in A not we that in ligand binding in only in A. of Aga16B-CBM6-2, in complex with neoagarohexaose, reveals the of direct interactions between the protein and ligand to the specificity by the with family 6 CBMs two and interactions with the non-reducing chains are to the the equivalent in CBM6 modules are in a with the and of the is with a between and in with family 6 CBMs where the are by M. Bolam D.N. A. J. Ferreira L.M. O. H. Black G.W. Henrissat B. Gilbert H.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Bolam D.N. Ferreira L.M. Henrissat B. A. Gilbert H.J. M. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). Indeed, in CBMs to are with the with which they interactions A.B. Bolam D.N. Gilbert H.J. Davies G.J. Biochem. J. 2004; 382: 769-781Crossref PubMed Scopus (1537) Google Scholar). is to that in one of the of a CBM binding to the are at with the this the equatorial to and of be at the of the of and with is with the that interactions are also likely to between the axial at and of most and the chains of CBMs, which are to the of the in the of the are interactions with the but the they they to the as J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). between and its ligand are to the at the non-reducing the O4 of the with the of both and and O3 a with the O3 and O4 of the also with the the of these interactions is have that in CBMs that with the target often has G. Williamson M.P. C. H. Gilbert H.J. Bolam D.N. 2003; PubMed Scopus Google Scholar, J. Bolam D.N. D. Williamson M.P. C. Davies G.J. Gilbert H.J. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). of is within with the of the of the two that they not a the of for in not the of the protein for its that interactions are the mechanism by which the to ligand binding. The of the the of the with the The of the and the interactions the O4 of the at the of the protein displays specificity for the non-reducing end of The with the axial O3 and equatorial O4 of the specificity for by the of as to such as and which are in plant structural polysaccharides and have equatorial O3 the which be at the non-reducing of by the of in which O3 is equatorial and O4 The in that with are and highly conserved equivalent to is in and in in the to bind agarose chains The in is in which not bind to the CBM this which a with and a role in this within the ligand binding The also that the which also with The of these interactions in likely in to a different which may the protein not of the in the that a role in the binding of these modules to the non-reducing of agarose chains the of family 6 that are likely to the disaccharide of the marine are and and in the are as and these contain a of which the and the modules of which a role in binding the non-reducing end of agarose By to the binding which to its ligand in may of agarose chains, and is that the binding in these modules be conserved in Aga16B-CBM6-2, and of in the role of in ligand the of the for in the of The that the the of ligand binding that a role in the recognition of by the of the of the in as a that with and a the not direct interactions with the by to the by which is to ligand recognition role in the binding of to the that the two their chains are in the CBMs that bind to is likely that the a role in ligand binding in these The role of the in CBM6 is to that of in which also to the by the that with the carbohydrate ligand H. Chem. Rev. 1998; PubMed Scopus Google Scholar), not with the not a role in the binding of the of CBMs to their recent have that are to carbohydrate recognition in two CBMs families and S. Boraston A.B. Davies G.J. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, D.N. H. Pell G. D. G. Henrissat B. Gilbert H.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus (69) Google Scholar). the a direct role in ligand recognition by the with the protein and the and O3 of a in the binding the mechanism by which the xylan recognition by the family CBM is currently the first that CBMs are able to bind to the non-reducing of agarose chains with specificity interactions with that that are to of the A ligand binding of family 6 CBMs into the structural for the different by these protein highly conserved and in Aga16B-CBM6-2, which to ligand binding binding are by the These between the different and the in ligand specificity by this family The binding CBM6 has a in in the to the of the which the is in the the of the is not this is also present in and which a role in the binding in both and a which the that to the of xylan chains in the between and the ligand into a with to the of the where of the non-reducing end of the is by with most with the of is in both and that the type C binding by these protein modules, the of the of the binding by the of also to the recognition of the non-reducing end of agarose chains by A that is to the CBM6 is in the of the protein in which is in binding the is to the ligand binding and to recognition is in to the which bind to and where this and in in to ligand binding. The of two CBMs in also in is are of glycoside hydrolases that contain CBMs, which ligand and is that these modules A.B. M. J. E. van J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, D.N. H. P. Simpson P.J. S.M. Williamson M.P. Gilbert H.J. PubMed Scopus Google Scholar). is that the in a by with agarose that for these is also that the in and bind to both chains in a agarose the of the two in such that they are not able to increasing their accessibility to the catalytic modules of these Indeed, that target which also displays a contain two but distinct binding and are and that these protein modules the two chains in S.M. Simpson P.J. Gilbert H.J. Williamson G. Williamson M.P. FEBS Lett. 1999; PubMed Scopus Google Scholar, T. Faulds B. Williamson G. J. Mol. Biol. PubMed Scopus Google Scholar). A has been for the non-catalytic binding in the catalytic of the A which is in a to the of the enzyme J. Henrissat B. M. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). is to that is that CBM6 of the enzyme to agarose that is distinct the polymer by the catalytic Indeed, is to that by binding to the end of agarose the CBM6 to the structure the that is not appended to the CBM to by the appended catalytic By contrast, the catalytic in is and to of its target is likely that the molecular of the the catalytic to access of agarose such that the in the substrate binding are with of catalytic modules, to CBMs that bind to the of polysaccharides, has been in two glycoside a that a which to the of both and xylan Boraston A.B. Kilburn D.G. PubMed Scopus Google Scholar), and in which the CBM6 to the non-reducing end of chains C. Gilbert H.J. Boraston A.B. J. Biol. Chem. 2005; 280: Full Text Full Text PDF PubMed Scopus Google Scholar). is glycoside hydrolases are by their CBMs to the of polysaccharides. is that these enzymes are to of the plant cell wall that have been to attack. areas of these recalcitrant may be highly and the CBMs are not targeting glycoside hydrolases to their target but of these that are amenable to enzyme attack. with

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.