Impact of the disulfide bond on hydrolytic characteristics of a xylanase from Talaromyces thermophiles F1208.

A xylanase from Talaromyces thermophiles F1208 (T-Xyn) was used specifically to explore the effects of disulfide bond on hydrolytic activity. The T-Xyn-C122S-C166S mutant does not have the C122-C166 disulfide bond present in wild-type T-Xyn, whereas T-Xyn-T38C-S50C and T-Xyn-T38C-S50C-C122S-C166S mutants have an introduced disulfide bond, C38-C50, to T-Xyn and T-Xyn-C122S-C166S, respectively. The optimum pH of T-Xyn-T38C-S50C and T-Xyn-T38C-S50C-C122S-C166S was lower than that of T-Xyn and T-Xyn-C122S-C166S. The introduction of a disulfide bond caused a decrease in the optimum temperature and thermal stability of T-Xyn. The existence of a disulfide bond has a strong influence on the hydrolysis characteristics of T-Xyn, which caused changes in the composition and proportion of the hydrolysate products. T-Xyn-T38C-S50C produces the highest level of xylose when using beechwood xylan as the substrate, whereas T-Xyn produces the highest level of xylobiose and T-Xyn-T38C-S50C-C122S-C166S produces the largest amount of xylotriose. When birchwood xylan was used as the substrate, the introduction of a disulfide bond increased the content of xylose, decreased the content of xylotriose and a high degree of polymerization (DP ≥ 5) was observed. The hydrolysis of oat-spelt xylan is more complex with the introduction of the disulfide bond causing an increase in the degradation rate of xylotriose.