title: Thermodynamic Relationships with Processivity in Serratia marcescens Family 18 Chitinases.
abstract: The enzymatic degradation of recalcitrant polysaccharides is accomplished by synergistic enzyme cocktails of glycoside hydrolases (GHs) and accessory enzymes. Many GHs are processive which means that they remain attached to the substrate in between subsequent hydrolytic reactions. Chitinases are GHs that catalyze the hydrolysis of chitin (β-1,4-linked N-acetylglucosamine). Previously, a relationship between active site topology and processivity has been suggested while recent computational efforts have suggested a link between the degree of processivity and ligand binding free energy. We have investigated these relationships by employing computational (molecular dynamics (MD)) and experimental (isothermal titration calorimetry (ITC)) approaches to gain insight into the thermodynamics of substrate binding to Serratia marcescens chitinases ChiA, ChiB, and ChiC. We show that increased processive ability indeed corresponds to more favorable binding free energy and that this likely is a general feature of GHs. Moreover, ligand binding in ChiB is entropically driven; in ChiC it is enthalpically driven, and the enthalpic and entropic contributions to ligand binding in ChiA are equal. Furthermore, water is shown to be especially important in ChiA-binding. This work provides new insight into oligosaccharide binding, getting us one step closer to understand how GHs efficiently degrade recalcitrant polysaccharides.
authors.affiliation: †Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. 5003, N-1432 Ås, Norway.
authors.forename: Anne Grethe
authors.initials: AG
authors.lastname: Hamre
authors.affiliation: ‡Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, United States.
authors.forename: Suvamay
authors.initials: S
authors.lastname: Jana
authors.affiliation: †Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. 5003, N-1432 Ås, Norway.
authors.forename: Matilde Mengkrog
authors.initials: MM
authors.lastname: Holen
authors.affiliation: †Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. 5003, N-1432 Ås, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Mathiesen
authors.affiliation: §Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia.
authors.forename: Priit
authors.initials: P
authors.lastname: Väljamäe
authors.affiliation: ‡Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506, United States.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Payne
authors.affiliation: †Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. 5003, N-1432 Ås, Norway.
authors.forename: Morten
authors.initials: M
authors.lastname: Sørlie
mesh_terms: D020134:Catalytic Domain; D002688:Chitinases / Q000737:chemistry* / Q000378:metabolism*; D019277:Entropy; D008024:Ligands; D056004:Molecular Dynamics Simulation; D012706:Serratia marcescens / Q000201:enzymology*
chemical_list: D008024:Ligands; D002688:Chitinases