Glycoside Hydrolase Family 116

This page is currently under construction. This means that the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information should be considered to be under revision and may be subject to major changes.

• Author: ^^^Beatrice Cobucci-Ponzano^^^
• Responsible Curator: ^^^Marco Moracci^^^

---

Glycoside Hydrolase Family GH116
Clan	none
Mechanism	retaining
Active site residues	known
CAZy DB link
http://www.cazy.org/GH116.html

Substrate specificities

This family of glycoside hydrolases was recently discovered characterising a new β-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus [1] and contains acid β-glucosidase (EC 3.2.1.45), β-glucosidase (EC 3.2.1.21) and β-xylosidase (EC 3.2.1.37) activities from the three domains of life. The β-glycosidase from S. solfataricus (SSO1353) is specific for the gluco- and xylosides β-bound to hydrophobic groups that are hydrolyzed by following a retaining reaction mechanism. SSO1353 is distantly related to the human non-lysosomal bile acid β-glucosidase GBA2, also known as glucocerebrosidase, involved in the catabolism of glucosylceramide, which is then converted to sphingomyelin [2]. SSO1353 has substrate specificity and inhibitor sensitivity slightly different from those of GBA2. In fact, the archaeal enzyme can hydrolyze both aryl β-gluco and β-xylosides and it is inhibited by both N-butyldeoxynojirimycin (NB-DNJ) and conduritol β-epoxide (CBE) [1]. Instead, GBA2 is inactive on methylumbellyferyl-β-D-xylopyranoside and is relatively insensitive to CBE [2].

Kinetics and Mechanism

The enzymes of this family are retaining glycoside hydrolases and follow the classical Koshland double-displacement mechanism [3]. The stereochemistry of hydrolysis has been demonstrated by ¹H-¹³C NMR spectroscopy analysis of the interglycosidic linkage of disaccharides formed by the transglycosylation action of SSO1353 with 4NP-β-Xyl [1].

Catalytic Residues

The catalytic residues were identified in the S. solfataricus β-glycosidase [1]. The catalytic nucleophile was identified as Glu335 through trapping of the 2- deoxy-2-fluoroglucosyl-enzyme intermediate and MS/MS analysis. The general acid/base catalyst role was assigned to Asp462 through mechanistic analysis of a mutant at that position, which included azide rescue experiments.

Three-dimensional structures

Unkwown

Family Firsts

First stereochemistry determination

S. solfataricus β-glycosidase by NMR [1].

First catalytic nucleophile identification

S. solfataricus β-glycosidase by 2-deoxy-2-fluoroglucose labeling [1].

First general acid/base residue identification

S. solfataricus β-glycosidase by azide rescue with mutant [1].

First 3-D structure

References

1. Cobucci-Ponzano B, Aurilia V, Riccio G, Henrissat B, Coutinho PM, Strazzulli A, Padula A, Corsaro MM, Pieretti G, Pocsfalvi G, Fiume I, Cannio R, Rossi M, and Moracci M. (2010). A new archaeal beta-glycosidase from Sulfolobus solfataricus: seeding a novel retaining beta-glycan-specific glycoside hydrolase family along with the human non-lysosomal glucosylceramidase GBA2. J Biol Chem. 2010;285(27):20691-703. DOI:10.1074/jbc.M109.086470 |
2. Boot RG, Verhoek M, Donker-Koopman W, Strijland A, van Marle J, Overkleeft HS, Wennekes T, and Aerts JM. (2007). Identification of the non-lysosomal glucosylceramidase as beta-glucosidase 2. J Biol Chem. 2007;282(2):1305-12. DOI:10.1074/jbc.M610544200 |

3. Koshland DE Jr: Stereochemistry and the mechanism of enzyme reactions. Biol Rev 1953, 28:416-436.