Abstact

BT_3567 protein, a putative β-glucosidase from Bacteroides thetaiotaomicron, exhibits higher activity toward Sop3-5 (Sopn , n: degree of polymerization of β-1,2-glucooligosaccharides) than toward Sop2 , unlike a known β-glucosidase from Listeria innocua which predominantly prefers Sop2 . In the complex structure determined by soaking of a D286N mutant crystal with Sop4 , a Sop3 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 Km values of the N81G mutant for Sop3-5 are much higher than those of the wild-type, suggesting that Asn81 contributes to the binding to substrates longer than Sop3 .