Crystal Structure of an Exo-1,5-α-l-arabinofuranosidase from Streptomyces avermitilis Provides Insights into the Mechanism of Substrate Discrimination between Exo- and Endo-type Enzymes in Glycoside Hydrolase Family 43*
摘要:
Exo-1,5-alpha-L-arabinofuranosidases belonging to glycoside hydrolase family 43 have strict substrate specificity. These enzymes hydrolyze only the alpha-1,5-linkages of linear arabinan and arabino-oligosaccharides in an exo-acting manner. The enzyme from Streptomyces avermitilis contains a core catalytic domain belonging to glycoside hydrolase family 43 and a C-terminal arabinan binding module belonging to carbohydrate binding module family 42. We determined the crystal structure of intact exo-1,5-alpha-L-arabinofuranosidase. The catalytic module is composed of a 5-bladed beta-propeller topologically identical to the other family 43 enzymes. The arabinan binding module had three similar subdomains assembled against one another around a pseudo-3-fold axis, forming a beta-trefoil-fold. A sugar complex structure with alpha-1,5-L-arabinofuranotriose revealed three subsites in the catalytic domain, and a sugar complex structure with alpha-L-arabinofuranosyl azide revealed three arabinose-binding sites in the carbohydrate binding module. A mutagenesis study revealed that substrate specificity was regulated by residues Asn-159, Tyr-192, and Leu-289 located at the aglycon side of the substrate-binding pocket. The exo-acting manner of the enzyme was attributed to the strict pocket structure of subsite -1, formed by the flexible loop region Tyr-281-Arg-294 and the side chain of Tyr-40, which occupied the positions corresponding to the catalytic glycon cleft of GH43 endo-acting enzymes.
Mechanism-based inhibition of GH127/146 cysteine glycosidases by stereospecifically functionalized l-arabinofuranosides
作者:Akihiro Ishiwata、Satoru Narita、Kenta Kimura、Katsunori Tanaka、Kiyotaka Fujita、Shinya Fushinobu、Yukishige Ito
DOI:10.1016/j.bmc.2022.117054
日期:2022.12
To understand the precise mechanism of the glycosidehydrolase (GH) family 127, a cysteine β-l-arabinofuranosidase (Arafase) – HypBA1 – has been isolated from Bifidobacterium longum in the human Gut microbiota, and the design and synthesis of the mechanism-based inhibitors such as l-Araf-haloacetamides have been carried out. The α-l-Araf-azide derivative was used as the monoglycosylamine equivalent
Crystal Structure of an Exo-1,5-α-l-arabinofuranosidase from Streptomyces avermitilis Provides Insights into the Mechanism of Substrate Discrimination between Exo- and Endo-type Enzymes in Glycoside Hydrolase Family 43*
Exo-1,5-alpha-L-arabinofuranosidases belonging to glycoside hydrolase family 43 have strict substrate specificity. These enzymes hydrolyze only the alpha-1,5-linkages of linear arabinan and arabino-oligosaccharides in an exo-acting manner. The enzyme from Streptomyces avermitilis contains a core catalytic domain belonging to glycoside hydrolase family 43 and a C-terminal arabinan binding module belonging to carbohydrate binding module family 42. We determined the crystal structure of intact exo-1,5-alpha-L-arabinofuranosidase. The catalytic module is composed of a 5-bladed beta-propeller topologically identical to the other family 43 enzymes. The arabinan binding module had three similar subdomains assembled against one another around a pseudo-3-fold axis, forming a beta-trefoil-fold. A sugar complex structure with alpha-1,5-L-arabinofuranotriose revealed three subsites in the catalytic domain, and a sugar complex structure with alpha-L-arabinofuranosyl azide revealed three arabinose-binding sites in the carbohydrate binding module. A mutagenesis study revealed that substrate specificity was regulated by residues Asn-159, Tyr-192, and Leu-289 located at the aglycon side of the substrate-binding pocket. The exo-acting manner of the enzyme was attributed to the strict pocket structure of subsite -1, formed by the flexible loop region Tyr-281-Arg-294 and the side chain of Tyr-40, which occupied the positions corresponding to the catalytic glycon cleft of GH43 endo-acting enzymes.