Aromatic-Mediated Carbohydrate Recognition in Processive Serratia marcescens Chitinases

• DOI: 10.1021/acs.jpcb.5b12610
• Publication Date: 2016-01-29T17:20:07Z
• Authors: Suvamay Jana; Anne Grethe Hamre; Patricia Wildberger; Matilde Mengkrog ...; Vincent G. H. Eij...; Gregg T. Beckham; Morten Sørlie; Christina M. Payne
• Keywords: Chitinase; Serratia

Microorganisms use a host of enzymes, including processive glycoside hydrolases, to deconstruct recalcitrant polysaccharides sugars. Processive hydrolases closely associate with polymer chains and repeatedly cleave glycosidic linkages without dissociating from the crystalline surface after each hydrolytic step; they are typically most abundant enzymes in both natural secretomes industrial cocktails by virtue their significant potential. The ubiquity aromatic residues lining enzyme catalytic tunnels clefts is notable feature hydrolases. We hypothesized that these have uniquely defined roles, such as substrate chain acquisition binding tunnel, local environment position relative center. Here, we investigated this hypothesis variants Serratia marcescens family 18 chitinases ChiA ChiB. applied molecular simulation free energy calculations assess active site dynamics ligand energies. Isothermal titration calorimetry provided further insight into enthalpic entropic contributions energy. Thus, roles six residues, Trp-167, Trp-275, Phe-396 ChiA, Trp-97, Trp-220, Phe-190 ChiB, been examined. observed point mutation tryptophan alanine results unfavorable changes wild-type. drastic effects were for positioned at "entrances" deep substrate-binding known be important processivity. Interestingly, phenylalanine mutations ChiB had little no effect on chito-oligomer binding, accordance limited removal chitinase functionality.