Transglycosylation reaction of xylanase B from the hyperthermophilic Thermotoga maritima with the ability of synthesis of tertiary alkyl β- d-xylobiosides and xylosides

Abstract

The recombinant xylanase B (XynB) of Thermotoga maritima MSB8 was characterized and was found to cleave p-nitrophenyl β- d-xyloside via the transglycosylation reaction in the previous study. XynB was activated in the presence of alcohols, and XynB activity was increased by iso-propanol (2 M) to 2.1-fold. This type of activation was investigated and was shown to be due to the transglycosylation activity with p-nitrophenyl β- d-xylobioside being converted to alkyl β- d-xylobiosides in the presence of XynB and alcohols. Through the transglycosylation reaction, alkyl β-xylosides and xylobiosides were simultaneously produced in the presence of xylan and alcohols. Primary alcohols were found to be the best acceptors. The highest yields of alkyl β-xylosides and xylobiosides were 33% and 50% of the total sugar, respectively. XynB showed a great ability to transfer xylose and xylobiose to secondary alcohol acceptors, and was unique for being able to synthesize the tertiary alkyl β-xylosides and xylobiosides with high yields of 18.2% and 11.6% of the total sugar, respectively. This is the first report of a xylanase with the ability to synthesize tertiary alkyl β-xylosides and xylobiosides. The specificity of the β-linkage was confirmed by the proton nuclear magnetic resonance ( 1 H NMR). Thus, XynB of T. maritima appears to be an ideal enzyme for the synthesis of useful alkyl β-xylosides and xylobiosides.