Xylanase from Marine Filamentous Fungus Pestalotiopsis sp. AN-7 Was Activated with Diluted Salt Solution Like Brackish Water

• Published in: Journal of Applied Glycoscience Vol. 68; no. 1; pp. 11 - 18
• Main Authors: Koh, Sangho, Mizuno, Masahiro, Izuoka, Yuto, Fujino, Naoto, Hamada-Sato, Naoko, Amano, Yoshihiko
• Format: Journal Article
• Language: English
• Published: Tsukuba The Japanese Society of Applied Glycoscience 11.03.2021; Japan Science and Technology Agency
• Subjects: Biodegradation; Brackish water; Calcium chloride; Cations; Deglycosylation; Divalent cations; Endophytes; Enzymatic activity; Enzyme activity; Fungi; GH10 xylanase; Glucan; Glycosidases; Glycoside hydrolase; Hydrolase; Magnesium chloride; Mangrove swamps; marine fungus; MeGlcA3Xyl3; Metal concentrations; metallic salt; N-glycosidase; Pestalotiopsis; pH effects; Potassium chloride; Proteins; Regular Paper; Saline solutions; Salts; Sodium chloride; Substrate specificity; Substrates; Thermal stability; Xylan; Xylanase; β-Glucan
• ISSN: 1344-7882; 1880-7291
• DOI: 10.5458/jag.jag.JAG-2020_0011

The genus Pestalotiopsis are endophytic fungi that have recently been identified as cellulolytic system producers. We herein cloned a gene coding for a xylanase belonging to glycoside hydrolase (GH) family 10 (PesXyn10A) from Pestalotiopsis sp. AN-7, which was isolated from the soil of a mangrove forest. This protein was heterologously expressed by Pichia pastoris as a host, and its enzymatic properties were characterized. PesXyn10A was produced as a glycosylated protein and coincident to theoretical molecular mass (35.3 kDa) after deglycosylation by peptide-N-glycosidase F. Purified recombinant PesXyn10A exhibited maximal activity at pH 6.0 and 50 °C, and activity was maintained at 90 % at pH 5.0 and temperatures lower than 30 °C for 24 h. The substrate specificity of PesXyn10A was limited and it hydrolyzed glucuronoxylan and arabinoxylan, but not β-glucan. The final hydrolysis products from birchwood xylan were xylose, xylobiose, and 1,23-α-D-(4-O-methyl-glucuronyl)-1,4-β-D-xylotriose. The addition of metallic salts (NaCl, KCl, MgCl2, and CaCl2) activated PesXyn10A for xylan degradation, and maximal activation by these divalent cations was approximately 160 % at a concentration of 5 mM. The thermostability of PesXyn10A significantly increased in the presence of 50 mM NaCl or 5 mM MgCl2. The present results suggest that the presence of metallic salts at a low concentration, similar to brackish water, exerts positive effects on the enzyme activity and thermal stability of PesXyn10A.