Structure and function of a glycoside hydrolase family 8 endoxylanase from Teredinibacter turnerae

TY - JOUR

T1 - Structure and function of a glycoside hydrolase family 8 endoxylanase from Teredinibacter turnerae

AU - Fowler, Claire A

AU - Hemsworth, Glyn R

AU - Cuskin, Fiona

AU - Hart, Sam

AU - Turkenburg, Johan

AU - Gilbert, Harry J.

AU - Walton, Paul H

AU - Davies, Gideon J

N1 - © 2018, The Author(s).

PY - 2018/10/5

Y1 - 2018/10/5

N2 - The biological conversion of lignocellulosic matter into high-value chemicals or biofuels is of increasing industrial importance as the sector slowly transitions away from nonrenewable sources. Many industrial processes involve the use of cellulolytic enzyme cocktails - a selection of glycoside hydrolases and, increasingly, polysaccharide oxygenases - to break down recalcitrant plant polysaccharides. ORFs from the genome of Teredinibacter turnerae, a symbiont hosted within the gills of marine shipworms, were identified in order to search for enzymes with desirable traits. Here, a putative T. turnerae glycoside hydrolase from family 8, hereafter referred to as TtGH8, is analysed. The enzyme is shown to be active against β-1,4-xylan and mixed-linkage (β-1,3,β-1,4) marine xylan. Kinetic parameters, obtained using high-performance anion-exchange chromatography with pulsed amperometric detection and 3,5-dinitrosalicyclic acid reducing-sugar assays, show that TtGH8 catalyses the hydrolysis of β-1,4-xylohexaose with a k cat/K m of 7.5 × 10 7  M -1  min -1 but displays maximal activity against mixed-linkage polymeric xylans, hinting at a primary role in the degradation of marine polysaccharides. The three-dimensional structure of TtGH8 was solved in uncomplexed and xylobiose-, xylotriose- and xylohexaose-bound forms at approximately 1.5 Å resolution; the latter was consistent with the greater k cat/K m for hexasaccharide substrates. A 2,5B boat conformation observed in the -1 position of bound xylotriose is consistent with the proposed conformational itinerary for this class of enzyme. This work shows TtGH8 to be effective at the degradation of xylan-based substrates, notably marine xylan, further exemplifying the potential of T. turnerae for effective and diverse biomass degradation.

AB - The biological conversion of lignocellulosic matter into high-value chemicals or biofuels is of increasing industrial importance as the sector slowly transitions away from nonrenewable sources. Many industrial processes involve the use of cellulolytic enzyme cocktails - a selection of glycoside hydrolases and, increasingly, polysaccharide oxygenases - to break down recalcitrant plant polysaccharides. ORFs from the genome of Teredinibacter turnerae, a symbiont hosted within the gills of marine shipworms, were identified in order to search for enzymes with desirable traits. Here, a putative T. turnerae glycoside hydrolase from family 8, hereafter referred to as TtGH8, is analysed. The enzyme is shown to be active against β-1,4-xylan and mixed-linkage (β-1,3,β-1,4) marine xylan. Kinetic parameters, obtained using high-performance anion-exchange chromatography with pulsed amperometric detection and 3,5-dinitrosalicyclic acid reducing-sugar assays, show that TtGH8 catalyses the hydrolysis of β-1,4-xylohexaose with a k cat/K m of 7.5 × 10 7  M -1  min -1 but displays maximal activity against mixed-linkage polymeric xylans, hinting at a primary role in the degradation of marine polysaccharides. The three-dimensional structure of TtGH8 was solved in uncomplexed and xylobiose-, xylotriose- and xylohexaose-bound forms at approximately 1.5 Å resolution; the latter was consistent with the greater k cat/K m for hexasaccharide substrates. A 2,5B boat conformation observed in the -1 position of bound xylotriose is consistent with the proposed conformational itinerary for this class of enzyme. This work shows TtGH8 to be effective at the degradation of xylan-based substrates, notably marine xylan, further exemplifying the potential of T. turnerae for effective and diverse biomass degradation.

KW - Biofuels

KW - Biomass

KW - Cellulolytic enzymes

KW - Glycoside hydrolase

KW - Marine polysaccharides

KW - Shipworms

KW - Teredinibacter turnerae

KW - Xylans/metabolism

KW - Plants/chemistry

KW - Polysaccharides/metabolism

KW - Gram-Negative Facultatively Anaerobic Rods/enzymology

KW - Gammaproteobacteria/enzymology

KW - Endo-1,4-beta Xylanases/chemistry

KW - Protein Conformation

KW - Bacterial Proteins/chemistry

KW - Kinetics

KW - Glycoside Hydrolases/chemistry

KW - Plant Cells/metabolism

UR - http://www.scopus.com/inward/record.url?scp=85054463209&partnerID=8YFLogxK

U2 - 10.1107/S2059798318009737

DO - 10.1107/S2059798318009737

M3 - Article

SN - 2059-7983

VL - 74

SP - 946

EP - 955

JO - Acta crystallographica. Section D, Structural biology

JF - Acta crystallographica. Section D, Structural biology

IS - Pt 10

ER -