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* Residue conservation analysis
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Enzyme class:
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E.C.3.2.1.4
- Cellulase.
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Reaction:
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Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.
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Gene Ontology (GO) functional annotation
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Biological process
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carbohydrate metabolic process
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1 term
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Biochemical function
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catalytic activity
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3 terms
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DOI no:
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J Mol Biol
320:303-309
(2002)
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PubMed id:
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A novel combination of two classic catalytic schemes.
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A.Shaw,
R.Bott,
C.Vonrhein,
G.Bricogne,
S.Power,
A.G.Day.
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ABSTRACT
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The crystal structure of an alkaline Bacillus cellulase catalytic core, from
glucoside hydrolase family 5, reveals a novel combination of the catalytic
machinery of two classic textbook enzymes. The enzyme has the expected two
glutamate residues in close proximity to one another in the active-site that are
typical of retaining cellulases. However, the proton donor, glutamate 139 is
also unexpectedly a member of a serine-histidine-glutamate catalytic triad,
forming a novel combination of catalytic machineries. Structure and sequence
analysis of glucoside hydrolase family 5 reveal that the triad is highly
conserved, but with variations at the equivalent of the serine position. We
speculate that the purpose of this novel catalytic triad is to control the
protonation of the acid/base glutamate, facilitating the first step of the
catalytic reaction, protonation of the substrate, by the proton donor glutamate.
If correct, this will be a novel use for a catalytic triad.
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Selected figure(s)
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Figure 1.
Figure 1. The stereoviews of the structure of the catalytic
domain of cellulase 103. (a) The electron density map of in the
active-site, including the catalytic triad, after heavy-atom
refinement and phasing using SHARP, and subsequent density
modification using SOLOMON.38 (b) Ribbons diagram of the
tertiary structure, with the catalytic triad and the Glu
nucleophile.
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Figure 2.
Figure 2. A comparison of the catalytic triads found in GH5
enzymes. (a) The type A triad from cellulase 103. (b) The type B
triad of exo-1,3-glucanase from Candida albicans.23 (c) The type
C triad of 1BQC; Thermobifida fusca b-mannanase.18
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2002,
320,
303-309)
copyright 2002.
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Literature references that cite this PDB file's key reference
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PubMed id
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Reference
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Y.Kitago,
S.Karita,
N.Watanabe,
M.Kamiya,
T.Aizawa,
K.Sakka,
and
I.Tanaka
(2007).
Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum.
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J Biol Chem, 282,
35703-35711.
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PDB codes:
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E.A.Zvereva,
T.V.Fedorova,
V.V.Kevbrin,
T.N.Zhilina,
and
M.L.Rabinovich
(2006).
Cellulase activity of a haloalkaliphilic anaerobic bacterium, strain Z-7026.
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Extremophiles, 10,
53-60.
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S.W.Hinz,
C.H.Doeswijk-Voragen,
R.Schipperus,
L.A.van den Broek,
J.P.Vincken,
and
A.G.Voragen
(2006).
Increasing the transglycosylation activity of alpha-galactosidase from Bifidobacterium adolescentis DSM 20083 by site-directed mutagenesis.
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Biotechnol Bioeng, 93,
122-131.
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A.Gutteridge,
and
J.M.Thornton
(2005).
Understanding nature's catalytic toolkit.
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Trends Biochem Sci, 30,
622-629.
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A.Haouz,
V.Vanheusden,
H.Munier-Lehmann,
M.Froeyen,
P.Herdewijn,
S.Van Calenbergh,
and
M.Delarue
(2003).
Enzymatic and structural analysis of inhibitors designed against Mycobacterium tuberculosis thymidylate kinase. New insights into the phosphoryl transfer mechanism.
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J Biol Chem, 278,
4963-4971.
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PDB codes:
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M.M.Sánchez,
F.I.Pastor,
and
P.Diaz
(2003).
Exo-mode of action of cellobiohydrolase Cel48C from Paenibacillus sp. BP-23. A unique type of cellulase among Bacillales.
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Eur J Biochem, 270,
2913-2919.
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The most recent references are shown first.
Citation data come partly from CiteXplore and partly
from an automated harvesting procedure. Note that this is likely to be
only a partial list as not all journals are covered by
either method. However, we are continually building up the citation data
so more and more references will be included with time.
Where a reference describes a PDB structure, the PDB
codes are
shown on the right.
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