Gene Expression and Molecular Characterization of a Xylanase from Chicken Cecum Metagenome

Abstract

A xylanase genexynAMG1with a 1,116-bp open reading frame, encoding an endo-β-1,4-xylanase, was cloned from a chicken cecum metagenome. The translatedXynAMG1protein consisted of 372 amino acids including a putative signal peptide of 23 amino acids. The calculated molecular mass of the matureXynAMG1was 40,013 Da, with a theoretical pI value of 5.76. The amino acid sequence ofXynAMG1showed 59% identity to endo-β-1,4-xylanase fromPrevotella bryantiiandPrevotella ruminicolaand 58% identity to that fromPrevotella copri.XynAMG1has two conserved motifs, DVVNE and TEXD, containing two active site glutamates and an invariant asparagine, characteristic of GH10 family xylanase. ThexynAMG1gene without signal peptide sequence was cloned and fused with thioredoxin protein (Trx.Tag) in pET-32a plasmid and overexpressed inEscherichia coliTuner™(DE3)pLysS. The purified matureXynAMG1was highly salt-tolerant and stable and displayed higher than 96% of its catalytic activity in the reaction containing 1 to 4 M NaCl. It was only slightly affected by common organic solvents added in aqueous solution to up to 5 M. This chicken cecum metagenome-derived xylanase has potential applications in animal feed additives and industrial enzymatic processes requiring exposure to high concentrations of salt and organic solvents.