title: Molecular cloning and expression of a novel β-glucosidase gene from Phialophora sp. G5.
abstract: A novel β-glucosidase gene, bgl1G5, was cloned from Phialophora sp. G5 and successfully expressed in Pichia pastoris. Sequence analysis indicated that the gene consists of a 1,431-bp open reading frame encoding a protein of 476 amino acids. The deduced amino acid sequence of bgl1G5 showed a high identity of 85% with a characterized β-glucosidase from Humicola grisea of glycoside hydrolase family 1. Compared with other fungal counterparts, Bgl1G5 showed similar optimal activity at pH 6.0 and 50 °C and was stable at pH 5.0-9.0. Moreover, Bgl1G5 exhibited good thermostability at 50 °C (6 h half-life) and higher specific activity (54.9 U mg⁻¹). The K (m) and V (max) values towards p-nitrophenyl β-D-glucopyranoside (pNPG) were 0.33 mM and 103.1 μmol min⁻¹ mg⁻¹, respectively. The substrate specificity assay showed that Bgl1G5 was highly active against pNPG, weak on p-nitrophenyl β-D-cellobioside (pNPC) and p-nitrophenyl-β-D-galactopyranoside (ONPG), and had no activity on cellobiose. This result indicated Bgl1G5 was a typical aryl β-glucosidase.
authors.affiliation: Key Laboratory of Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing 100081, People's Republic of China.
authors.forename: Xuejun
authors.initials: X
authors.lastname: Li
authors.forename: Junqi
authors.initials: J
authors.lastname: Zhao
authors.forename: Pengjun
authors.initials: P
authors.lastname: Shi
authors.forename: Peilong
authors.initials: P
authors.lastname: Yang
authors.forename: Yaru
authors.initials: Y
authors.lastname: Wang
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
mesh_terms: D003001:Cloning, Molecular; D010676:Phialophora / Q000201:enzymology*; D001617:beta-Glucosidase / Q000378:metabolism*
chemical_list: D001617:beta-Glucosidase