Improving special hydrolysis characterization into Talaromyces thermophilus F1208 xylanase by engineering of N-terminal extension and site-directed mutagenesis in C-terminal.

The purpose of this study was to gain insights into the hydrolysis characteristics of xylanase in producing xylo-oligosaccharides and to improve these by protein engineering. In this study, a hybrid enzyme (T-XynFM) was created from Talaromyces thermophilus F1208 xylanase (T-Xyn) by replacement of the N-terminal extension Phe1-Pro16 with Ala1-Gln8 and substitution of amino acid Phe193 (185) with Ser in the C-terminal. The enzyme showed optimum activity at 55°C and pH 6.5. Its residual activity was more than 55% after treatment at 50°C, pH 6.5 for 12h Km values of T-XynFM for beechwood xylan, birchwood xylan, and oat-spelt xylan were 10.31, 10.03, and 8.90mgmL-1, respectively. The enzyme displayed special hydrolysis characteristics: almost no xylose was produced on using xylotriose (X3), xylotetraose (X4), and xylopentaose as substrates. Moreover, over 60% X4 existed in hydrolyzed products of X3, indicating that T-XynFM possesses formidable transglycosylation properties.