Characterization of Neoagarooligosaccharide Hydrolase BpGH117 from a Human Gut Bacterium Bacteroides plebeius

Abstract

alpha-Neoagarobiose (NAB)/neoagarooligosaccharide (NAO) hydrolase plays an important role as an exo-acting 3,6-anhydro-alpha-(1,3)-L-galactosidase in agarose utilization. Agarose is an abundant polysaccharide found in red seaweeds, comprising 3,6-anhydro-L-galactose (AHG) and D-galactose residues. Unlike agarose degradation, which has been reported in marine microbes, recent metagenomic analysis of Bacteroides plebeius, a human gut bacterium, revealed the presence of genes encoding enzymes involved in agarose degradation, including alpha-NAB/NAO hydrolase. Among the agarolytic enzymes, BpGH117 has been partially characterized. Here, we characterized the exo-acting alpha-NAB/NAO hydrolase BpGH117, originating from B. plebeius. The optimal temperature and pH for His-tagged BpGH117 activity were 35 degrees C and 9.0, respectively, indicative of its unique origin. His-tagged BpGH117 was thermostable up to 35 degrees C, and the enzyme activity was maintained at 80% of the initial activity at a pre-incubation temperature of 40 degrees C for 120 min. K-m and V-max values for NAB were 30.22 mM and 54.84 U/mg, respectively, and k(cat)/K-m was 2.65 s(-1) mM(-1). These results suggest that His-tagged BpGH117 can be used for producing bioactive products such as AHG and agarotriose from agarose efficiently.