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Difference between revisions of "Glycoside Hydrolase Family 36"

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== Kinetics and Mechanism ==
 
== Kinetics and Mechanism ==
Family GH36 alpha-galactosidases are retaining enzymes, as first shown by NMR <cite>1</cite> and follow a classical Koshland double-displacement mechanism. Enzymes that have been well-studied kinetically include the ''Cellulomonas fimi'' endo-glycanase (Cex)'''*''', for which a detailed kinetic study involving both steady state and pre-steady state kinetic analyses was performed <cite>2</cite>.  Recent studies of the roles of each substrate hydroxyl in catalysis have also been described <cite>3</cite>. Detailed analyses of substrate and subsite specificities of the ''Pseudomonas cellulosa'' xylanase have also been described <cite>4</cite>.
+
Family GH36 alpha-galactosidases are anomeric configuration-retaining enzymes, like their [[Glycoside Hydrolase Family 36 (GH36)|Family GH27]] relatives in Clan GH-D, as first shown by NMR <cite>1</cite>. In addition to NMR data, mutagenesis and azide rescue experiments in this study <cite>1</cite> established that Clan GH-D enzymes in both GH27 and GH36 use a classical Koshland double-displacement mechanism. Enzymes that have been well-studied kinetically include the ''Cellulomonas fimi'' endo-glycanase (Cex)'''*''', for which a detailed kinetic study involving both steady state and pre-steady state kinetic analyses was performed <cite>2</cite>.  Recent studies of the roles of each substrate hydroxyl in catalysis have also been described <cite>3</cite>. Detailed analyses of substrate and subsite specificities of the ''Pseudomonas cellulosa'' xylanase have also been described <cite>4</cite>.
  
  
 
== Catalytic Residues ==
 
== Catalytic Residues ==
The catalytic nucleophile was first identified in the ''Cellulomonas fimi'' endo-xylanase (CfXyn10A) as Glu233 (earlier numbered as 274) in the sequence IT'''<u>E</u>'''LD through trapping of the 2-deoxy-2-fluoroglucosyl-enzyme intermediate and subsequent peptide mapping <cite>5</cite>. The acid/base catalyst was first identified as Glu127 in this same enzyme through detailed mechanistic analysis of mutants at that position, which included azide rescue experiments <cite>6</cite>. Family GH10 enzymes, as is typical of [http://www.cazy.org/fam/acc_GH.html#table Clan GHA], have an asparagine residue preceding the acid/base catalyst in a typical NEP sequence. The asparagine engages in important hydrogen bonding interactions with the substrate 2-hydroxyl.
+
 
  
 
== Three-dimensional structures ==
 
== Three-dimensional structures ==
Three-dimensional structures are available for a large number of Family GH10 enzymes, the first solved being those of the ''Streptomyces lividans'' xylanase A <cite>7</cite> and the ''C. fimi'' endo-glycanase Cex <cite>8</cite>. As members of Clan GHA they have a classical (&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>9</cite>.
 
 
 
''PICTURES?  OVERALL STRUCTURE; ACTIVE SITE; CARTOON OF ACTIVE SITE SHOWING INTERACTIONS?''
 
 
  
==== For example: ====
 
* 3-D Structure of Bruce Stone:
 
[[Image:Bruce_stone_150x180.jpg]]
 
  
* Link to a XET structure picture:
 
** http://www.rcsb.org/pdb/explore/explore.do?structureId=1UMZ
 
  
 
== Family Firsts ==
 
== Family Firsts ==
 
;First sterochemistry determination: ''Thermotoga maritima'' alpha-galactosidase, by NMR <cite>1</cite>.
 
;First sterochemistry determination: ''Thermotoga maritima'' alpha-galactosidase, by NMR <cite>1</cite>.
;First catalytic nucleophile identification: ''Thermotoga maritima'' alpha-galactosidase, by structural homology and rescue kinetics with mutants <cite>1</cite>
+
;First catalytic nucleophile identification: ''Sulfolobus solfataricus'' alpha-galactosidase GalS, by sequence homology with GH27 enzymes and mutagenesis <cite>3</cite>.  Subsequently confirmed in ''Thermotoga maritima'' alpha-galactosidase by structural homology, mutagenesis, and azide rescue <cite>1</cite>.
;First general acid/base residue identification: ''Thermotoga maritima'' alpha-galactosidase, by structural homology and rescue kinetics with mutants <cite>1</cite>
+
;First general acid/base residue identification: ''Sulfolobus solfataricus'' alpha-galactosidase GalS, by sequence homology with GH27 enzymes and mutagenesis <cite>3</cite>.  Subsequently confirmed in ''Thermotoga maritima'' alpha-galactosidase by structural homology, mutagenesis, and azide rescue <cite>1</cite>.
;First 3-D structure: ''Thermotoga maritima'' alpha-galactosidase.  Coordinates first reported as part of a high-throughput functional genomics project <cite>2</cite>, structural alignment with GH27 enzymes indicated structure/function homology within Clan GH-D <cite>1</cite>.
+
;First 3-D structure: ''Thermotoga maritima'' alpha-galactosidase.  Coordinates first reported as part of a high-throughput functional genomics project <cite>2</cite>, structural analysis reported in ref. <cite>1</cite>.
  
 
== References ==
 
== References ==
 
<biblio>
 
<biblio>
 
#1 pmid=17323919
 
#1 pmid=17323919
#2 pmid=8193153
+
#2 pmid=12193646
#3 pmid=IN Press
+
#3 pmid=16547025
#4 pmid=10767281
+
#4 Sinnott, M.L. (1990) Catalytic mechanisms of enzymatic glycosyl transfer. Chem. Rev. 90, 1171-1202. [http://dx.doi.org/10.1021/cr00105a006 DOI: 10.1021/cr00105a006]
#5 pmid=1678739
+
 
#6 pmid=7910761
+
 
#7 pmid=8063693
 
#8 pmid=7918478
 
#9 pmid=7624375
 
 
</biblio>
 
</biblio>
  
 
[[Category:Glycoside Hydrolase Families]]
 
[[Category:Glycoside Hydrolase Families]]

Revision as of 12:03, 27 May 2007

Glycoside Hydrolase Family GH36
Clan GH-D
Mechanism retaining
Active site residues known
CAZy DB link
http://www.cazy.org/fam/GH36.html

Substrate specificities

Alpha-galactosidase and alpha-N-acetylgalactosaminidase activity has been demonstrated in archaeal, bacterial, and eukaryotic members of this family. Additionally, certain plant members of this family possess stachyose synthase or raffinose synthase activity.

Kinetics and Mechanism

Family GH36 alpha-galactosidases are anomeric configuration-retaining enzymes, like their Family GH27 relatives in Clan GH-D, as first shown by NMR [1]. In addition to NMR data, mutagenesis and azide rescue experiments in this study [1] established that Clan GH-D enzymes in both GH27 and GH36 use a classical Koshland double-displacement mechanism. Enzymes that have been well-studied kinetically include the Cellulomonas fimi endo-glycanase (Cex)*, for which a detailed kinetic study involving both steady state and pre-steady state kinetic analyses was performed [2]. Recent studies of the roles of each substrate hydroxyl in catalysis have also been described [3]. Detailed analyses of substrate and subsite specificities of the Pseudomonas cellulosa xylanase have also been described [4].


Catalytic Residues

Three-dimensional structures

Family Firsts

First sterochemistry determination
Thermotoga maritima alpha-galactosidase, by NMR [1].
First catalytic nucleophile identification
Sulfolobus solfataricus alpha-galactosidase GalS, by sequence homology with GH27 enzymes and mutagenesis [3]. Subsequently confirmed in Thermotoga maritima alpha-galactosidase by structural homology, mutagenesis, and azide rescue [1].
First general acid/base residue identification
Sulfolobus solfataricus alpha-galactosidase GalS, by sequence homology with GH27 enzymes and mutagenesis [3]. Subsequently confirmed in Thermotoga maritima alpha-galactosidase by structural homology, mutagenesis, and azide rescue [1].
First 3-D structure
Thermotoga maritima alpha-galactosidase. Coordinates first reported as part of a high-throughput functional genomics project [2], structural analysis reported in ref. [1].

References

  1. Comfort DA, Bobrov KS, Ivanen DR, Shabalin KA, Harris JM, Kulminskaya AA, Brumer H, and Kelly RM. (2007). Biochemical analysis of Thermotoga maritima GH36 alpha-galactosidase (TmGalA) confirms the mechanistic commonality of clan GH-D glycoside hydrolases. Biochemistry. 2007;46(11):3319-30. DOI:10.1021/bi061521n | PubMed ID:17323919 [1]
  2. Lesley SA, Kuhn P, Godzik A, Deacon AM, Mathews I, Kreusch A, Spraggon G, Klock HE, McMullan D, Shin T, Vincent J, Robb A, Brinen LS, Miller MD, McPhillips TM, Miller MA, Scheibe D, Canaves JM, Guda C, Jaroszewski L, Selby TL, Elsliger MA, Wooley J, Taylor SS, Hodgson KO, Wilson IA, Schultz PG, and Stevens RC. (2002). Structural genomics of the Thermotoga maritima proteome implemented in a high-throughput structure determination pipeline. Proc Natl Acad Sci U S A. 2002;99(18):11664-9. DOI:10.1073/pnas.142413399 | PubMed ID:12193646 [2]
  3. Brouns SJ, Smits N, Wu H, Snijders AP, Wright PC, de Vos WM, and van der Oost J. (2006). Identification of a novel alpha-galactosidase from the hyperthermophilic archaeon Sulfolobus solfataricus. J Bacteriol. 2006;188(7):2392-9. DOI:10.1128/JB.188.7.2392-2399.2006 | PubMed ID:16547025 [3]
  4. Sinnott, M.L. (1990) Catalytic mechanisms of enzymatic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006

    [4]

All Medline abstracts: PubMed