| Structural highlights
Function
[CAH_THEMA] Esterase that removes acetyl groups from a number of O-acetylated small substrates, such as acetylated xylose, short xylo-oligosaccharides and cephalosporin C. Has no activity towards polymeric acetylated xylan, 4-methylumbelliferyl acetate or alpha-naphthyl acetate. Able to catalyze rapid hydrolysis of a range of substrates preferably with acetate groups, independent of the alcohol moiety. Exhibits a narrow selectivity for short chain acyl esters (C2-C3). Displays broad substrate specificity by hydrolyzing acetate at 2, 3, and 4 positions of 4-nitrophenyl-beta-D-xylopyranoside (pNP-Xyl) with similar efficiency. Cannot cleave amide linkages.[1] [2] [3]
Publication Abstract from PubMed
The carbohydrate esterase family 7 (CE7) belonging to the alpha/beta hydrolase superfamily contains a structurally conserved loop extension element relative to the canonical alpha/beta hydrolase fold. This element called the beta-interface loop contributes 20-30% of the total buried surface area at intersubunit interfaces of the functional hexameric state. To test whether this loop is an enabling region for the structure and function of the oligomeric assembly, we designed a truncation variant of the thermostable CE7 acetyl esterase from Thermotoga maritima (TmAcE). Although deletion of 26 out of 40 residues in the loop had little impact on the hexamer formation, the variant exhibited altered dynamics of the oligomeric assembly and a loss of thermal stability. Furthermore, the mutant lacked catalytic activity. Crystal structures of the variant and a new crystal form of the wild type protein determined at 2.75A and 1.76A, respectively, provide a rationale for the properties of the variant. The hexameric assembly in the variant is identical to that of the wild type and differed only in the lack of buried surface area interactions at the original intersubunit interfaces. This is accompanied by disorder in an extended region of the truncated loop that consequently induces disorder in the neighboring oxyanion hole loop. Overall, the results suggest that the beta-interface loop in CE7 enzymes is dispensable for the oligomeric assembly. Rather, the loop extension event was evolutionarily selected to regulate activity, conformational flexibility and thermal stability.
An extended loop in CE7 carbohydrate esterase family is dispensable for oligomerization but required for activity and thermostability.,Singh MK, Manoj N J Struct Biol. 2016 Jun;194(3):434-45. doi: 10.1016/j.jsb.2016.04.008. Epub 2016 , Apr 13. PMID:27085421[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Drzewiecki K, Angelov A, Ballschmiter M, Tiefenbach KJ, Sterner R, Liebl W. Hyperthermostable acetyl xylan esterase. Microb Biotechnol. 2010 Jan;3(1):84-92. doi: 10.1111/j.1751-7915.2009.00150.x., Epub 2009 Sep 18. PMID:21255309 doi:http://dx.doi.org/10.1111/j.1751-7915.2009.00150.x
- ↑ Levisson M, Han GW, Deller MC, Xu Q, Biely P, Hendriks S, Ten Eyck LF, Flensburg C, Roversi P, Miller MD, McMullan D, von Delft F, Kreusch A, Deacon AM, van der Oost J, Lesley SA, Elsliger MA, Kengen SW, Wilson IA. Functional and structural characterization of a thermostable acetyl esterase from Thermotoga maritima. Proteins. 2012 Jan 27. doi: 10.1002/prot.24041. PMID:22411095 doi:10.1002/prot.24041
- ↑ Hedge MK, Gehring AM, Adkins CT, Weston LA, Lavis LD, Johnson RJ. The structural basis for the narrow substrate specificity of an acetyl esterase from Thermotoga maritima. Biochim Biophys Acta. 2012 Sep;1824(9):1024-30. doi:, 10.1016/j.bbapap.2012.05.009. Epub 2012 Jun 1. PMID:22659119 doi:http://dx.doi.org/10.1016/j.bbapap.2012.05.009
- ↑ Singh MK, Manoj N. An extended loop in CE7 carbohydrate esterase family is dispensable for oligomerization but required for activity and thermostability. J Struct Biol. 2016 Jun;194(3):434-45. doi: 10.1016/j.jsb.2016.04.008. Epub 2016 , Apr 13. PMID:27085421 doi:http://dx.doi.org/10.1016/j.jsb.2016.04.008
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