Glycoside Hydrolase Family 67 - Revision history

Harry Brumer: /* Substrate specificities = */

2018-02-27T01:54:21Z

Substrate specificities =

Harry Gilbert: /* Kinetics and Mechanism */

2018-02-19T22:54:14Z

Kinetics and Mechanism

Harry Gilbert: /* Family Firsts */

2018-02-19T22:53:18Z

Family Firsts

Harry Gilbert: /* Three-dimensional structures */

2018-02-19T22:51:25Z

Three-dimensional structures

Harry Gilbert: /* Catalytic Residues */

2018-02-19T22:50:24Z

Catalytic Residues

Harry Gilbert: /* Kinetics and Mechanism */

2018-02-19T22:48:27Z

Kinetics and Mechanism

Harry Gilbert: /* References */

2018-02-19T22:47:53Z

References

Harry Gilbert: /* Substrate specificities = */

2018-02-19T22:46:44Z

Substrate specificities =

Harry Gilbert: /* Substrate specificities = */

2018-02-19T22:45:53Z

Substrate specificities =

Harry Gilbert: /* Substrate specificities */

2018-02-19T22:44:43Z

Substrate specificities

@@ Line 24: / Line 24: @@
 </div>
-= Substrate specificities ==
+== Substrate specificities ==
 [[Glycoside hydrolase]]s of this family display alpha-glucuronidase activity. The enzymes target the glucuronic acid appended to the C2-OH of the xylose at the non-reducing end of xylooligosaccharides. The enzymes display a preference for 4-O-methyl-D-glucuronic acid side chains. The length of the oligosaccharide does not influence catalytic rate indicating that the enzyme only interacts with the uronic acid and the linked xylose. These enzymes do not remove glucuronic acid from internal regions of xylan <cite>Ruile1995,Bronnenmeier1995</cite>. The enzymes are generally intracellular or membrane associated <cite>Shulami1999,Nagy2002</cite> suggesting  that they play a terminal role in uncapping decorated xyloooligosaccharides, making these molecules available to beta-xylosidases produced by the host.

@@ Line 28: / Line 28: @@
 == Kinetics and Mechanism ==
-Alpha-glucuronidases are [[inverting]] enzymes that hydrolyse their target glycoside bond through a single displacement mechanism assisted by [[general acid]] and [[general base]] residues. Thus the glucuronic acid is formed in a beta configuration <cite>Biely2000</cite>.
+&alpha;-glucuronidases are [[inverting]] enzymes that hydrolyse their target glycoside bond through a single displacement mechanism assisted by [[general acid]] and [[general base]] residues. Thus the glucuronic acid is formed in a beta configuration <cite>Biely2000</cite>.
 == Catalytic Residues ==

@@ Line 37: / Line 37: @@
 == Family Firsts ==
-;First sterochemistry determination: <sup>1</sup>H NMR demonstrated that the released 4-methyl-D-glucuronic acid was a beta anomer and thus that the enzyme is an inverter <cite>#5</cite>.
+;First sterochemistry determination: <sup>1</sup>H NMR demonstrated that the released 4-methyl-D-glucuronic acid was a beta anomer and thus that the enzyme is an inverter <cite>Biely2000</cite>.
-;First [[general base]] residue identification: The general base was suggested by mutagenesis studies only and there remains two potential candidates <cite>#8</cite>
+;First [[general base]] residue identification: The general base was suggested by mutagenesis studies only and there remains two potential candidates <cite>Zaide2001</cite>
-;First [[general acid]] residue identification: The general acid residue was suggested by mutagenesis studies <cite>#8</cite>
+;First [[general acid]] residue identification: The general acid residue was suggested by mutagenesis studies <cite>Zaide2001</cite>
-;First 3-D structure: Two reports on the crystal structure of GH67 glucuronidases were published within 18 months of each other <cite>#6#7</cite>
+;First 3-D structure: Two reports on the crystal structure of GH67 glucuronidases were published within 18 months of each other <cite>Nurizzo2002,Golan2004</cite>
 == References ==

@@ Line 34: / Line 34: @@
 == Three-dimensional structures ==
-GH67 enzymes contain three distinct domains <cite>#6#7</cite>. The N-terminal domain forms a two-layer β sandwich, the central domain, the catalytic domain, is a classical (β/α)8 barrel whose catalytic center is located on the opposite, "C-terminal" side of the barrel to the N-terminal domain. The remaining, C-terminal domain is mainly α-helical. It wraps around the catalytic domain, making additional interactions both with the N-terminal domain of its parent monomer and also forming the majority of the dimer-surface with the equivalent C-terminal domain of the other monomer of the dimer. The active site comprises a deep, partially hydrophobic, pocket.
+GH67 enzymes contain three distinct domains <cite>Nurizzo2002,Golan2004</cite>. The N-terminal domain forms a two-layer β sandwich, the central domain, the catalytic domain, is a classical (β/α)8 barrel whose catalytic center is located on the opposite, "C-terminal" side of the barrel to the N-terminal domain. The remaining, C-terminal domain is mainly α-helical. It wraps around the catalytic domain, making additional interactions both with the N-terminal domain of its parent monomer and also forming the majority of the dimer-surface with the equivalent C-terminal domain of the other monomer of the dimer. The active site comprises a deep, partially hydrophobic, pocket.
 == Family Firsts ==

@@ Line 31: / Line 31: @@
 == Catalytic Residues ==
-Typical of [[inverting]] glycoside hydrolases, GH67 enzymes contain a [[general acid]] that protonates the scissile glycosidic oxygen promoting leaving group departure. This residue, Glu292 in the ''Cellvibrio japonicus'' GH67 <cite>#6</cite> and Glu285 in the ''Geobacillus stearothermophilus'' GH67 enzymes <cite>#7</cite> is a conserved glutamate within GH67. There are a pair of carboxylic acids that make hydrogen bonds with the catalytic water (attacks the anomeric carbon of the scissile glycosidic bond), and are predicted to activate the solvent molecule, thus acting as the [[general base]]. Which of these highly conserved residues, Glu393/Asp365 and Glu392/Asp364 in the ''C. japonicus'' and ''G. stearothermophilus'' enzymes, respectively, act as the [[general base]] is unclear. Mutational studies suggested that Asp365 in the ''C. japonicus'' enzyme may be the catalytic base <cite>#6</cite>, although similar mutagenesis studies on the ''Geobacillus'' glucuronidase indicate that mutation of either possible catalytic bases results in almost complete inactivation of the enzyme <cite>#8</cite>.
+Typical of [[inverting]] glycoside hydrolases, GH67 enzymes contain a [[general acid]] that protonates the scissile glycosidic oxygen promoting leaving group departure. This residue, Glu292 in the ''Cellvibrio japonicus'' GH67 <cite>Nurizzo2002</cite> and Glu285 in the ''Geobacillus stearothermophilus'' GH67 enzymes <cite>Golan2004</cite> is a conserved glutamate within GH67. There are a pair of carboxylic acids that make hydrogen bonds with the catalytic water (attacks the anomeric carbon of the scissile glycosidic bond), and are predicted to activate the solvent molecule, thus acting as the [[general base]]. Which of these highly conserved residues, Glu393/Asp365 and Glu392/Asp364 in the ''C. japonicus'' and ''G. stearothermophilus'' enzymes, respectively, act as the [[general base]] is unclear. Mutational studies suggested that Asp365 in the ''C. japonicus'' enzyme may be the catalytic base <cite>Nurizzo2002</cite>, although similar mutagenesis studies on the ''Geobacillus'' glucuronidase indicate that mutation of either possible catalytic bases results in almost complete inactivation of the enzyme <cite>Zaide2001</cite>.
 == Three-dimensional structures ==

@@ Line 44: / Line 44: @@
 == References ==
 <biblio>
-#Rulie1995 pmid=9044261
+#Ruile1995 pmid=9044261
 #Bronnenmeier1995 pmid=7496513
 #Shulami1999 pmid=10368143

@@ Line 25: / Line 25: @@
 = Substrate specificities ==
-[[Glycoside hydrolase]]s of this family display alpha-glucuronidase activity. The enzymes target the glucuronic acid appended to the C2-OH of the xylose at the non-reducing end of xylooligosaccharides. The enzymes display a preference for 4-O-methyl-D-glucuronic acid side chains. The length of the oligosaccharide does not influence catalytic rate indicating that the enzyme only interacts with the uronic acid and the linked xylose. These enzymes do not remove glucuronic acid from internal regions of xylan <cite>Ruile1997,Bronnenmeier1995</cite>. The enzymes are generally intracellular or membrane associated <cite>Shulami1999,Nagy2002</cite> suggesting  that they play a terminal role in uncapping decorated xyloooligosaccharides, making these molecules available to beta-xylosidases produced by the host.
+[[Glycoside hydrolase]]s of this family display alpha-glucuronidase activity. The enzymes target the glucuronic acid appended to the C2-OH of the xylose at the non-reducing end of xylooligosaccharides. The enzymes display a preference for 4-O-methyl-D-glucuronic acid side chains. The length of the oligosaccharide does not influence catalytic rate indicating that the enzyme only interacts with the uronic acid and the linked xylose. These enzymes do not remove glucuronic acid from internal regions of xylan <cite>Rulie1997,Bronnenmeier1995</cite>. The enzymes are generally intracellular or membrane associated <cite>Shulami1999,Nagy2002</cite> suggesting  that they play a terminal role in uncapping decorated xyloooligosaccharides, making these molecules available to beta-xylosidases produced by the host.
 == Kinetics and Mechanism ==