Glycoside Hydrolase Family 134 - Revision history

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References

Spencer Williams at 06:09, 3 February 2018

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Harry Brumer at 15:37, 12 December 2016

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Harry Brumer at 15:37, 12 December 2016

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Spencer Williams at 04:22, 11 December 2016

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Spencer Williams at 04:21, 11 December 2016

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 {{CuratorApproved}}
-* [[Author]]: ^^^Spencer Williams^^^
+* [[Author]]: [[User:Spencer Williams|Spencer Williams]]
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 <biblio>
 #Shimizu2015 pmid=26385921
-#Jin2016 [http://dx.doi.org/10.1021/acscentsci.6b00232 DOI:10.1021/acscentsci.6b00232]
+#Jin2016 pmid=28058278
 </biblio>
 [[Category:Glycoside Hydrolase Families|GH134]]

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 == Substrate specificities ==
-[[Glycoside hydrolase]] family 134 exclusively contains β-1,4-mannanases, and was created based on the discovery of Man134A from ''Aspergillus nidulans'' <cite>Shimizu2015</cite>. Man134A exhibited weak activity on galactomannan but robust activity on glucomannan, and activity on β-1,4-linked mannopentaose and hexaose <cite>Shimizu2015</cite>. ''Ss''GH134 from ''Streptomyces'' sp. NRRL B-24484 possessed a strong preference for unsubstituted linear β-mannans over gluco- and galactomannans <cite>Jin2016</cite>. ''Ss''GH134 possessed activity on β-1,4-linked mannotetraose, pentaose and hexaose.
+[[Glycoside hydrolase]] family 134 exclusively contains β-1,4-mannanases, and was created based on the discovery of Man134A from ''Aspergillus nidulans'' <cite>Shimizu2015</cite>. Man134A exhibits weak activity on galactomannan but robust activity on glucomannan, and activity on β-1,4-linked mannopentaose and hexaose <cite>Shimizu2015</cite>. ''Ss''GH134 from ''Streptomyces'' sp. NRRL B-24484 possesses a strong preference for unsubstituted linear β-mannans over gluco- and galactomannans <cite>Jin2016</cite>. ''Ss''GH134 possesses activity on β-1,4-linked mannotetraose, pentaose and hexaose.
 == Kinetics and Mechanism ==

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 Structural analysis of ''Ss''GH134 from ''Streptomyces'' sp. (see below) suggested roles for Glu45 as a [[general acid]] catalyst and for Asp57 as a [[general base]] catalyst <cite>Jin2016</cite>. These roles were supported by mutagenesis with the corresponding Glu45Ala and Asp57Ala single mutants inactive on β-mannopentaose and hexaose.
 == Three-dimensional structures ==
-The three dimensional structure was first reported for ''Ss''GH134, and exists as a mixed α-helix/β-sheet fold with resemblance to HEWL ([[GH22]]), as well as [[GH19]] chitinases, [[GH23]] G-type lysozyme, and [[GH124]] cellulases <cite>Jin2016</cite>. A binary Michaelis complex of the E45A variant of ''Ss''GH134 with mannopentaose bound in the active site defined the -3 to +2 subsites, and showed the sugar binding in the -1 subsite in a <sup>1</sup>''C''<sub>4</sub> conformation; a similar conformation was observed for the reducing-end mannose of a complex of mannotriose bound to the -3 to -1 subsites of wild-type ''Ss''GH134 <cite>Jin2016</cite>. Within the Michaelis complex, the carboxylate of the highly conserved C-terminal residue Ile173 is hydrogen bonded to O6 of the –2 mannosyl unit, and also forms a salt-bridge with the highly conserved K59. Within only the Michaelis complex, this interaction results in the formation of an active cleft tunnel reminiscent of processive glycoside hydrolases; the C-terminal segment is disordered in both ''apo'' and mannotriose product-bound forms <cite>Jin2016</cite>. ''Ss''GH134 can be classified as a ''[[syn/anti lateral protonation|syn]]'' protonator, with the acid residue situated ''syn'' to the C1-O5 bond.
+The three dimensional structure was first reported for ''Ss''GH134, and exists as a mixed α-helix/β-sheet fold with resemblance to HEWL ([[GH22]]), as well as [[GH19]] chitinases, [[GH23]] G-type lysozyme, and [[GH124]] cellulases <cite>Jin2016</cite>. A binary Michaelis complex of the E45A variant of ''Ss''GH134 with mannopentaose bound in the active site defined the -3 to +2 subsites, and showed the sugar binding in the -1 subsite in a <sup>1</sup>''C''<sub>4</sub> conformation; a similar conformation was observed for the reducing-end mannose of a complex of mannotriose bound to the -3 to -1 subsites of wild-type ''Ss''GH134 <cite>Jin2016</cite>. Within the Michaelis complex, the carboxylate of the highly conserved C-terminal residue Ile173 is hydrogen bonded to O6 of the –2 mannosyl unit, and also forms a salt-bridge with the highly conserved K59. Within only the Michaelis complex, this interaction results in the formation of an active cleft tunnel reminiscent of processive glycoside hydrolases; the C-terminal segment is disordered in both ''apo'' and mannotriose product-bound forms <cite>Jin2016</cite>. ''Ss''GH134 can be classified as a [[syn/anti lateral protonation|''syn'' protonator]], with the acid residue situated ''syn'' to the C1-O5 bond.
 == Family Firsts ==
 ;First stereochemistry determination: ''Ss''GH134 was shown to be [[inverting]] by <sup>1</sup>H NMR spectroscopy <cite>Jin2016</cite>.

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 == Kinetics and Mechanism ==
-<sup>1</sup>H NMR spectroscopic analysis of ''Ss''GH134 catalyzed cleavage of a benzoylhydrazine derivative of β-mannohexaose provided evidence for the formation of the α-anomer, consistent with an [[inverting]] mechanism <cite>Jin2016</cite>. Crystallographic evidence from binary complexes of ''Ss''GH134 with substrate and product, complemented by quantum mechanics/molecular mechanics calculations, supports a ''southern hemisphere'' <sup>1</sup>''C''<sub>4</sub>→<sup>3</sup>''H''<sub>4</sub><sup>‡</sup>→<sup>3</sup>''S''<sub>1</sub> [[conformational itinerary]] along the reaction coordinate <cite>Jin2016</cite>.
+<sup>1</sup>H NMR spectroscopic analysis of ''Ss''GH134 catalyzed cleavage of a benzoylhydrazine derivative of β-mannohexaose provided evidence for the formation of the α-anomer, consistent with an [[inverting]] mechanism <cite>Jin2016</cite>. Crystallographic evidence from binary complexes of ''Ss''GH134 with substrate and product, complemented by quantum mechanics/molecular mechanics calculations, supports a "southern hemisphere" <sup>1</sup>''C''<sub>4</sub>→<sup>3</sup>''H''<sub>4</sub><sup>‡</sup>→<sup>3</sup>''S''<sub>1</sub> [[conformational itinerary]] along the reaction coordinate <cite>Jin2016</cite>.
 == Catalytic Residues ==