Function and structure relationships of a β‐1,2‐glucooligosaccharide‐degrading β‐glucosidase

BT _3567 protein, a putative β‐glucosidase from Bacteroides thetaiotaomicron , exhibits higher activity toward Sop 3–5 (Sop n , n: degree of polymerization of β‐1,2‐glucooligosaccharides) than toward Sop 2 , unlike a known β‐glucosidase from Listeria innocua which predominantly prefers Sop 2 . In the complex structure determined by soaking of a D286N mutant crystal with Sop 4 , a Sop 3 moiety was observed at subsites −1 to +2. The glucose moiety at subsite +2 forms a hydrogen bond with Asn81, which is replaced with Gly in the L. innocua β‐glucosidase. The K m values of the N81G mutant for Sop 3–5 are much higher than those of the wild‐type, suggesting that Asn81 contributes to the binding to substrates longer than Sop 3 .