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

Abstract

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.