title: A β-Mannanase with a Lysozyme-like Fold and a Novel Molecular Catalytic Mechanism.
abstract: The enzymatic cleavage of β-1,4-mannans is achieved byendo-β-1,4-mannanases, enzymes involved in germination of seeds and microbial hemicellulose degradation, and which have increasing industrial and consumer product applications. β-Mannanases occur in a range of families of the CAZy sequence-based glycoside hydrolase (GH) classification scheme including families 5, 26, and 113. In this work we reveal that β-mannanases of the newly described GH family 134 differ from other mannanase families in both their mechanism and tertiary structure. A representative GH family 134endo-β-1,4-mannanase from aStreptomycessp. displays a fold closely related to that of hen egg white lysozyme but acts with inversion of stereochemistry. A Michaelis complex with mannopentaose, and a product complex with mannotriose, reveal ligands with pyranose rings distorted in an unusual inverted chair conformation.Ab initioquantum mechanics/molecular mechanics metadynamics quantified the energetically accessible ring conformations and provided evidence in support of a1C4→3H4‡→3S1conformational itinerary along the reaction coordinate. This work, in concert with that on GH family 124 cellulases, reveals how the lysozyme fold can be co-opted to catalyze the hydrolysis of different polysaccharides in a mechanistically distinct manner.
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York , Heslington, YO10 5DD, U.K.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jin
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute and Department of Medical Biology, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Marija
authors.initials: M
authors.lastname: Petricevic
authors.affiliation: ACRF Chemical Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3010, Australia; School of Chemistry and Bio21 Molecular Science and Biotechnology Institute and Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Alan
authors.initials: A
authors.lastname: John
authors.affiliation: Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) & IQTCUB, Universitat de Barcelona , 08028 Barcelona, Spain.
authors.forename: Lluís
authors.initials: L
authors.lastname: Raich
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York , Heslington, YO10 5DD, U.K.
authors.forename: Huw
authors.initials: H
authors.lastname: Jenkins
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York , Heslington, YO10 5DD, U.K.
authors.forename: Leticia
authors.initials: L
authors.lastname: Portela De Souza
authors.affiliation: Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University , Framlington Place, Newcastle upon Tyne NE2 4HH, U.K.
authors.forename: Fiona
authors.initials: F
authors.lastname: Cuskin
authors.affiliation: Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University , Framlington Place, Newcastle upon Tyne NE2 4HH, U.K.
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Gilbert
authors.affiliation: Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) & IQTCUB, Universitat de Barcelona, 08028 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), 08020 Barcelona, Spain.
authors.forename: Carme
authors.initials: C
authors.lastname: Rovira
authors.affiliation: ACRF Chemical Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3010, Australia; School of Chemistry and Bio21 Molecular Science and Biotechnology Institute and Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Ethan D
authors.initials: ED
authors.lastname: Goddard-Borger
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute and Department of Medical Biology, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York , Heslington, YO10 5DD, U.K.
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies