• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.159-165
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• 2007

An extracellular xylanase from the brown-rot fungus Fomitopsis palustris grown on rice straw culture was purified to a single protein band. On SDS-PAGE, the molecular mass of purified enzyme was estimated to be about 43 kDa. The amino acid sequence of the proteolytic fragments showed high homology with fungal glycoside hydrolase family 10 xylanases. The $K_m$, $K_{cat}$ and $V_{max}$ for birch xylan were $31mg/m{\ell}$, $2.3{\times}10^4/min$ and 252.3 U/mg, respectively. The optimal activity of the purified xylanase from F palustris was observed at pH 4.0~5.0 and $70^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.32 no.8
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• pp.1064-1071
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• 2022

Arabinogalactans have diverse biological properties and can be used as pharmaceutical agents. Most arabinogalactans are composed of β-(1→3)-galactan, so it is particularly important to identify β-1,3-galactanases that can selectively degrade them. In this study, a novel exo-β-1,3-galactanase, named PoGal3, was screened from Penicillium oxalicum sp. 68, and hetero-expressed in P. pastoris GS115 as a soluble protein. PoGal3 belongs to glycoside hydrolase family 43 (GH43) and has a 1,356-bp gene length that encodes 451 amino acids residues. To study the enzymatic properties and substrate selectivity of PoGal3, β-1,3-galactan (AG-P-I) from larch wood arabinogalactan (LWAG) was prepared and characterized by HPLC and NMR. Using AG-P-I as substrate, purified PoGal3 exhibited an optimal pH of 5.0 and temperature of 40℃. We also discovered that Zn²⁺ had the strongest promoting effect on enzyme activity, increasing it by 28.6%. Substrate specificity suggests that PoGal3 functions as an exo-β-1,3-galactanase, with its greatest catalytic activity observed on AG-P-I. Hydrolytic products of AG-P-I are mainly composed of galactose and β-1,6-galactobiose. In addition, PoGal3 can catalyze hydrolysis of LWAG to produce galacto-oligomers. PoGal3 is the first enzyme identified as an exo-β-1,3-galactanase that can be used in building glycan blocks of crucial glycoconjugates to assess their biological functions.