Linked Life Data

10869182

Source:http://linkedlifedata.com/resource/pubmed/id/10869182

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
26
pubmed:dateCreated
2000-8-10
pubmed:abstractText
The enzymes from the alpha-amylase family all share a similar alpha-retaining catalytic mechanism but can have different reaction and product specificities. One family member, cyclodextrin glycosyltransferase (CGTase), has an uncommonly high transglycosylation activity and is able to form cyclodextrins. We have determined the 2.0 and 2.5 A X-ray structures of E257A/D229A CGTase in complex with maltoheptaose and maltohexaose. Both sugars are bound at the donor subsites of the active site and the acceptor subsites are empty. These structures mimic a reaction stage in which a covalent enzyme-sugar intermediate awaits binding of an acceptor molecule. Comparison of these structures with CGTase-substrate and CGTase-product complexes reveals three different conformational states for the CGTase active site that are characterized by different orientations of the centrally located residue Tyr 195. In the maltoheptaose and maltohexaose-complexed conformation, CGTase hinders binding of an acceptor sugar at subsite +1, which suggests an induced-fit mechanism that could explain the transglycosylation activity of CGTase. In addition, the maltoheptaose and maltohexaose complexes give insight into the cyclodextrin size specificity of CGTases, since they precede alpha-cyclodextrin (six glucoses) and beta-cyclodextrin (seven glucoses) formation, respectively. Both ligands show conformational differences at specific sugar binding subsites, suggesting that these determine cyclodextrin product size specificity, which is confirmed by site-directed mutagenesis experiments.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
4
pubmed:volume
39
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7772-80
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Structures of maltohexaose and maltoheptaose bound at the donor sites of cyclodextrin glycosyltransferase give insight into the mechanisms of transglycosylation activity and cyclodextrin size specificity.
pubmed:affiliation
Center for Carbohydrate Bioengineering and Laboratory of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't