View source for Glycoside Hydrolase Family 30

{{CuratorApproved}}
* [[Author]]: [[User:Brian Rempel|Brian Rempel]]
* [[Responsible Curator]]:  [[User:Steve Withers|Stephen Withers]]
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<div style="float:right">
{| {{Prettytable}}
|-
|{{Hl2}} colspan="2" align="center" |'''Glycoside Hydrolase Family 30'''
|-
|'''Clan'''   
|GH-A
|-
|'''Mechanism'''
|retaining
|-
|'''Active site residues'''
|known
|-
|{{Hl2}} colspan="2" align="center" |'''CAZy DB link'''
|-
| colspan="2" |http://www.cazy.org/fam/GH30.html
|}
</div>

==Substrate specificities==
This family contains [[glycoside hydrolases]] with three known enzyme activities: &beta;-glucosylceramidase, &beta;-1,6-glucanase, and &beta;-xylosidase. This family enzymes currently contains enzymes from only bacteria and eukaryotes. The best-studied enzyme is human &beta;-glucocerebrosidase whose deficiency causes Gauchers disease <cite>#1</cite>. This enzyme is responsible for hydrolyzing the &beta;-glucoside from the glycolipid glucosylceramide.

==Kinetics and Mechanism==
Family GH30 enzymes are [[retaining]] enzymes. Although this has never been formally demonstrated experimentally through NMR analysis of the initially formed sugar product, covalent trapping of the enzymatic nucleophile (described below) conclusively demonstrates that these enzymes follow the classic [[Koshland double-displacement mechanism]]. The &beta;-glucosylceramidases require an activator protein and negatively charged phospholipids for optimal activity, <cite>#2</cite> although the role of these activators is still not entirely clear. Neither the &beta;-1,6-glucanases <cite>#3</cite> nor the &beta;-xylosidases <cite>#4</cite> appear to require any activators.

==Catalytic Residues==
The [[catalytic nucleophile]] was first identified in human &beta;-glucocerebrosidase as Glu340 in the sequence FAS<u>'''E'''</u>A by trapping of the 2-deoxy-2-fluoro-glucosyl-enzyme [[intermediate]] and subsequent peptide mapping by LC/MS-MS <cite>#5</cite>. The [[catalytic nucleophile]] had been previously mistakenly identified as Asp443 using a tritiated bromoconduritol epoxide <cite>#6 #7</cite>, although subsequent kinetic analyses of site-directed mutants of Asp443 were not consistent with its role as the catalytic nucleophile <cite>#8</cite>. The [[general acid/base]] residue of human &beta;-glucoerebrosidase is predicted to be Glu-274 <cite>#9</cite>. While this identification has not been experimentally verified through analysis of variant proteins created by mutation of that site, it is consistent with structural studies (below).

==Three-dimensional structures==
The three-dimensional structure of human &beta;-glucocerebrosidase was first solved in 2003 <cite>#10</cite>, and since then several different structures of this enzyme have been reported (reviewed in <cite>#11</cite>). GH30 enzymes are members of the GHA clan fold, consistent with the classic (&alpha;/&beta;)<sub>8</sub> TIM barrel fold with the two key active site glutamic acids located at the C-terminal ends of &beta;-strands 4 (acid/base) and 7 (nucleophile) <cite>#12</cite>.

==Family Firsts==
                                                            
;'''First [[catalytic nucleophile]] identification'''
:Human &beta;-glucocerebrosidase by 2-fluoroglucose labelling <cite>#1</cite>
;'''First 3-D structure of a GH30 enzyme'''
:Human &beta;-glucocerebrosidase <cite>#2</cite>

==References==
<biblio>
#1 pmid=19094956
#2 pmid=2127241
#3 pmid=12162562
#4 pmid=11909624
#5 pmid=7908905
#6 pmid=3456607
#7 pmid=2077872
#8 pmid=8294487
#9 pmid=9134434
#10 pmid=12792654
#11 pmid=18783340
#12 pmid=7624375
</biblio>

[[Category:Glycoside Hydrolase Families|GH030]]