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/K of 7.5 × 10 M min 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/K for hexasaccharide substrates. A B 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.