Linked Life Data

1827439

Source:http://linkedlifedata.com/resource/pubmed/id/1827439

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
14
pubmed:dateCreated
1991-6-10
pubmed:abstractText
An active-site peptide containing an aspartic acid implicated in catalysis has been isolated and sequenced from two Streptococcus sobrinus extracellular glucosyltransferases: sucrose:1,3-alpha-D-glucan 3-alpha-D-glucosyltransferase (GTase-I) and sucrose:1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase (GTase-S). The sequenced peptides, tagged with radiolabeled glucose, were isolated from a pepsin digest of a stabilized glucosylenzyme complex prepared by rapidly denaturing a reaction of enzyme and radiolabeled sucrose. The glucosyl linkage had previously been characterized as a beta-anomer bound to an active-site carboxyl group. Purified GTase-I and GTase-S glucosyl-peptides had the following similar but not identical sequences: GTase-I, Asp-Ser-Ile-Arg-Val-Asp-Ala-Val-Asp; and GTase-S, Asp-Gly-Val-Arg-Val-Asp-Ala-Val-Asp. Each has 3 aspartic acids as potential sites of glucose conjugation, but the relevant residue was not identified in sequence analysis because the highly base-labile glucosyl bond was cleaved in the first sequence cycle. As an alternative, the GTase-I glucosyl-peptide was partially digested at the N terminus with cathepsin C and at the C terminus with carboxypeptidase P. Analysis of the truncated products by fast atom bombardment mass spectrometry localized the glucosyl group to Asp-6 i the GTase-I peptide. In the native enzyme, this sequence is found near the N terminus, well-removed from the glucan-binding site located on a 60-kDa domain at the C terminus. The catalysis-dependent method of incorporating a glucosyl label implicates the aspartic acid as the residue involved in stabilizing an oxocarbonium ion transition state. The peptide segment is highly conserved and homologous to a peptide from sucrase-isomaltase labeled by site-directed irreversible inhibition and peptide segments common to a broad array of alpha-glucosidases and related transferases.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
266
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8916-22
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Isolation and sequence of an active-site peptide containing a catalytic aspartic acid from two Streptococcus sobrinus alpha-glucosyltransferases.
pubmed:affiliation
Department of Basic Sciences, School of Dentistry, University of Southern California, Los Angeles 90089-0641.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.