title: The Structure of an Archaeal β-Glucosaminidase Provides Insight into Glycoside Hydrolase Evolution.
abstract: The archaeal exo-β-d-glucosaminidase (GlmA) is a dimeric enzyme that hydrolyzes chitosan oligosaccharides into monomer glucosamines. GlmA is a member of the glycosidase hydrolase (GH)-A superfamily-subfamily 35 and is a novel enzyme in terms of its primary structure. Here, we present the crystal structure of GlmA in complex with glucosamine at 1.27 Å resolution. The structure reveals that a monomeric form of GlmA shares structural homology with GH42 β-galactosidases, whereas most of the spatial positions of the active site residues are identical to those of GH35 β-galactosidases. We found that upon dimerization, the active site of GlmA changes shape, enhancing its ability to hydrolyze the smaller substrate in a manner similar to that of homotrimeric GH42 β-galactosidase. However, GlmA can differentiate glucosamine from galactose based on one charged residue while using the "evolutionary heritage residue" it shares with GH35 β-galactosidase. Our study suggests that GH35 and GH42 β-galactosidases evolved by exploiting the structural features of GlmA.
authors.affiliation: From the Biomedical Research Institute (BMD), National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, s-mine@aist.go.jp.
authors.forename: Shouhei
authors.initials: S
authors.lastname: Mine
authors.affiliation: the Research Institute for Sustainable Chemistry (ISC), AIST, 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, and masa-watanabe@aist.go.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: the Research Institute for Sustainable Chemistry (ISC), AIST, 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, and.
authors.forename: Saori
authors.initials: S
authors.lastname: Kamachi
authors.affiliation: the Laboratory of Protein Structure, Function and Design, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Abe
authors.affiliation: the Laboratory of Protein Structure, Function and Design, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ueda
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005944:Glucosamine / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism; D006596:Hexosaminidases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D043902:Pyrococcus horikoshii / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D013379:Substrate Specificity; D019712:Thermococcus / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism
chemical_list: D006026:Glycoside Hydrolases; D006596:Hexosaminidases; C064499:exo-beta-D-glucosaminidase; D005944:Glucosamine
keywords: X-ray crystallography; archaea; evolution; galactose; glucosamine; glycoside hydrolase