Journal of Applied Glycoscience
Online ISSN : 1880-7291
Print ISSN : 1344-7882
ISSN-L : 1344-7882
Characterization of a GH family 43 β-xylosidase having a novel carbohydrate-binding module from Paenibacillus xylaniclasticus strain TW1
Daichi ItoEmiri NakanoShuichi KaritaMidori Umekawa Khanok RatanakhanockchaiChakrit Tachaapaikoon
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JOURNAL OPEN ACCESS Advance online publication

Article ID: jag.JAG-2022_0001

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Abstract

Paenibacillus xylaniclasticus strain TW1, a gram-positive facultative anaerobic bacterium, was isolated as a xylanolytic microorganism from the wastes of a pineapple processing factory. A gene encoding one of its xylanolytic enzymes, a β-xylosidase, was cloned and sequenced. Sequence analysis revealed that this β-xylosidase, named PxXyl43A, was composed of a glycoside hydrolase (GH) family 43 subfamily 12 catalytic module and an unknown function module (UM). The full-length PxXyl43A (PxXyl43A) was heterologously expressed in Escherichia coli and purified. Recombinant PxXyl43A exhibited hydrolysis activity against both p-nitrophenyl-β-D xylopyranoside (pNPX) and p-nitrophenyl-α-L-arabinofuranoside at specific activities of 250 mU/mg and 310 mU/mg, respectively. The optimal reaction pH and temperature for pNPX hydrolysis were 7.1 and 54 °C, respectively. At pH 7.0 and 54 °C, the Km and kcat for pNPX were 1.2 mM and 2.8 ± 0.15 s-1, respectively. It was also discovered that the recombinant unknown function module of PxXyl43A (PxXyl43A-UM) could bind to insoluble xylans like birchwood xylan and oat spelt xylan, whereas it did not bind to cellulosic substrates such as ball-milled cellulose, carboxymethyl cellulose or lichenan. The PxXyl43A-UM’s binding constant value Ka for oat spelt xylan was 2.0 × 10-5 M-1. These results suggest that PxXyl43A possesses a novel carbohydrate-binding module, named as CBMx, specific for xylan-containing polysaccharides.

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© 2022, by The Japanese Society of Applied Glycoscience
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