User:Pedro Coutinho

2009-11-06T00:14:52Z

Pedro Coutinho:

User:Pedro Coutinho

2009-11-06T00:14:01Z

Pedro Coutinho:

2009-11-05T21:53:23Z

Pedro Coutinho: /* Family Firsts */

{{UnderConstruction}}
* [[Author]]: ^^^Pedro Coutinho^^^
* [[Responsible Curator]]: ^^^Pedro Coutinho^^^
----


<div style="float:right">
{| {{Prettytable}}
|-
|{{Hl2}} colspan="2" align="center" |'''Glycoside Hydrolase Family GH15'''
|-
|'''Clan'''
|GH-L
|-
|'''Mechanism'''
|inverting
|-
|'''Active site residues'''
|known
|-
|{{Hl2}} colspan="2" align="center" |'''CAZy DB link'''
|-
| colspan="2" |http://www.cazy.org/fam/GH15.html
|}
</div>


== Substrate specificities ==
Enzymes from this family hydrolyze the non-reducing end of a-glucosides by an inverting mechanism. At present, the most commonly characterized activity is glucoamylase (EC 3.2.1.3), also know as amyloglucosidase, but glucodextranase (EC 3.2.1.70) and α,α-trehalase (EC 3.2.1.28) activities have been described. It has been found that fungal glucoamylases present some substrate flexibility and are able to degrade not only α-1,4-glycosidic bonds but also α-1,6-, α-1,3- and α-1,2-bonds to a lower degree <cite>Meagher1989</cite>.

== Kinetics and Mechanism ==

Family GH15 α-glycosidases are inverting enzymes, as first shown by Weil et al., 1954 <cite>Weil1954</cite> and follow a classical Koshland simple-displacement mechanism. Enzymes that have been well studied kinetically include ''Aspergillus'' and ''Rhizopus'' glucoamylases.

== Catalytic Residues ==

The general acid was first identified in the ''Aspergillus awamori'' / ''Aspergillus niger ''glucoamylase as Glu179 following site-directed mutagenesis <cite>Sierks1990</cite>. The general base was defined as Glu400 following the three-dimensional structure determination <cite>Harris1993</cite> and confirmed later on by site directed mutagenesis and kinetic studies <cite>Frandsen1994</cite>. Simultaneously the general base was identified in ''Clostridium'' sp. G0005 glucoamylase by chemical modification and mutagenesis <cite>Ohnishi1994</cite>.

== Three-dimensional structures ==

Three-dimensional structures are available for a number of number of family GH15 enzymes, the first solved being that of ''Aspergillus awamori'' var. X100 glucoamylase <cite>Aleshin1992</cite>. All members of this family have (a/a)<sub>6</sub> barrel fold with the two key catalytic glutamic acid residues being approximately 200 residues apart in sequence and located at the loops following barrel α-helices 5 (general acid) and 11 (general base). Bacterial GH15 enzymes have in general an all β-strand super-β-sandwich preceding the catalytic (α/α)<sub>6</sub> barrel <cite>Aleshin2003</cite>.

== Family Firsts ==
;First sterochemistry determination:
Inverting mechanism in glucoamylase described by Weil ''et al.'', 1954 <cite>Weil1954</cite>.

;First sequence identification:
''Aspergillus niger'' glucoamylase by peptide sequencing <cite>Svensson1983</cite>.
;First [[general acid]] identification:
''Aspergillus niger'' glucoamylase from mutant kinetic analysis <cite>Sierks1990</cite>.

;First [[general base]] identification:
''Aspergillus awamori'' var. X100 glucoamylase from crystal structure <cite>Harris1993</cite>.

;First 3-D structure:
''Aspergillus awamori'' var. X100 glucoamylase by X-ray cristallography <cite>Aleshin1992</cite>.

== References ==
<biblio>
#Weil1954 Weil CE, Burch RJ, Van Dyk JW. An α-amyloglucosidase that produces β-glucose, Cereal Chem 1954; 31 150–158.
#Meagher1989 pmid=18588153
#Sierks1990 pmid=1970434
#Aleshin1992 pmid=1527049
#Harris1993 pmid=8431441
#Ohnishi1994 pmid=7906268
#Frandsen1994 pmid=7947792

</biblio>


<nowiki>[[Category:Glycoside Hydrolase Families|GHnnn]]</nowiki>

Glycoside Hydrolase Family 15

2009-11-05T21:31:54Z

Pedro Coutinho:

{{UnderConstruction}}
* [[Author]]: ^^^Pedro Coutinho^^^
* [[Responsible Curator]]: ^^^Pedro Coutinho^^^
----


<div style="float:right">
{| {{Prettytable}}
|-
|{{Hl2}} colspan="2" align="center" |'''Glycoside Hydrolase Family GH15'''
|-
|'''Clan'''
|GH-L
|-
|'''Mechanism'''
|inverting
|-
|'''Active site residues'''
|known
|-
|{{Hl2}} colspan="2" align="center" |'''CAZy DB link'''
|-
| colspan="2" |http://www.cazy.org/fam/GH15.html
|}
</div>


== Substrate specificities ==
Enzymes from this family hydrolyze the non-reducing end of a-glucosides by an inverting mechanism. At present, the most commonly characterized activity is glucoamylase (EC 3.2.1.3), also know as amyloglucosidase, but glucodextranase (EC 3.2.1.70) and α,α-trehalase (EC 3.2.1.28) activities have been described. It has been found that fungal glucoamylases present some substrate flexibility and are able to degrade not only α-1,4-glycosidic bonds but also α-1,6-, α-1,3- and α-1,2-bonds to a lower degree <cite>Meagher1989</cite>.

== Kinetics and Mechanism ==

Family GH15 α-glycosidases are inverting enzymes, as first shown by Weil et al., 1954 <cite>Weil1954</cite> and follow a classical Koshland simple-displacement mechanism. Enzymes that have been well studied kinetically include ''Aspergillus'' and ''Rhizopus'' glucoamylases.

== Catalytic Residues ==

The general acid was first identified in the ''Aspergillus awamori'' / ''Aspergillus niger ''glucoamylase as Glu179 following site-directed mutagenesis <cite>Sierks1990</cite>. The general base was defined as Glu400 following the three-dimensional structure determination <cite>Harris1993</cite> and confirmed later on by site directed mutagenesis and kinetic studies <cite>Frandsen1994</cite>. Simultaneously the general base was identified in ''Clostridium'' sp. G0005 glucoamylase by chemical modification and mutagenesis <cite>Ohnishi1994</cite>.

== Three-dimensional structures ==

Three-dimensional structures are available for a number of number of family GH15 enzymes, the first solved being that of ''Aspergillus awamori'' var. X100 glucoamylase <cite>Aleshin1992</cite>. All members of this family have (a/a)<sub>6</sub> barrel fold with the two key catalytic glutamic acid residues being approximately 200 residues apart in sequence and located at the loops following barrel α-helices 5 (general acid) and 11 (general base). Bacterial GH15 enzymes have in general an all β-strand super-β-sandwich preceding the catalytic (α/α)<sub>6</sub> barrel <cite>Aleshin2003</cite>.

== Family Firsts ==
;First sterochemistry determination:
Inverting mechanism in glucoamylase described by Weil ''et al.'', 1954 <cite>Weil1954</cite>.

;First [[general base]] identification:
''Aspergillus awamori'' var. X100 glucoamylase from crystal structure <cite>Harris1993</cite>.

;First [[general acid]] residue identification:
''Aspergillus niger'' glucoamylase from mutant kinetic analysis <cite>Sierks1990</cite>.

;First 3-D structure:
''Aspergillus awamori'' var. X100 glucoamylase by X-ray cristallography <cite>Aleshin1992</cite>.

== References ==
<biblio>
#Weil1954 Weil CE, Burch RJ, Van Dyk JW. An α-amyloglucosidase that produces β-glucose, Cereal Chem 1954; 31 150–158.
#Meagher1989 pmid=18588153
#Sierks1990 pmid=1970434
#Aleshin1992 pmid=1527049
#Harris1993 pmid=8431441
#Ohnishi1994 pmid=7906268
#Frandsen1994 pmid=7947792

</biblio>


<nowiki>[[Category:Glycoside Hydrolase Families|GHnnn]]</nowiki>