Linked Life Data

7906142

Source:http://linkedlifedata.com/resource/pubmed/id/7906142

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
1994-3-22
pubmed:abstractText
The distinct roles of the two magnesium ions essential to the activity of D-xylose isomerase from Streptomyces olivochromogenes were examined. The enzyme-magnesium complex was isolated, and the stoichiometry of cation binding determined by neutron activation analysis to be 2 mol of magnesium per mole of enzyme. A plot of Mg2+ added versus Mg2+ bound to enzyme is consistent with apparent KD values of < or = 0.5-1.0 mM for one Mg2+ and < or = 2-5 mM for the second. A site-directed mutant of D-xylose isomerase was designed to remove the tighter, tetracoordinated magnesium binding site (site 1, Mg-1); Glu180 was replaced with Lys180. The stoichiometry of metal binding to this mutant, E180K, is 1 mol of magnesium per mole of enzyme. Ring-opening assays with 1-thioglucose (H2S released upon ring opening) show E180K catalyzes the opening of the sugar ring at 20% the rate of the wild-type, but E180K does not catalyze isomerization of glucose to fructose. Thus, the magnesium bound to Glu180 is essential for isomerization but not essential for ring opening. The X-ray crystallographic structures of E180K in the absence of magnesium and in the presence and absence of 250 mM glucose were obtained to 1.8-A resolution and refined to R factors of 17.7% and 19.7%, respectively. The wild-type and both E180K structures show no significant structural differences, except the epsilon-amino group of Lys180, which occupies the position usually occupied by the Mg-1.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
33
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1488-94
pubmed:dateRevised
2011-11-17
pubmed:meshHeading
pubmed-meshheading:7906142-Aldose-Ketose Isomerases, pubmed-meshheading:7906142-Amino Acids, pubmed-meshheading:7906142-Base Sequence, pubmed-meshheading:7906142-Binding Sites, pubmed-meshheading:7906142-Carbohydrate Epimerases, pubmed-meshheading:7906142-Carbohydrate Metabolism, pubmed-meshheading:7906142-Catalysis, pubmed-meshheading:7906142-Cations, Divalent, pubmed-meshheading:7906142-Crystallography, X-Ray, pubmed-meshheading:7906142-Glutamates, pubmed-meshheading:7906142-Glutamic Acid, pubmed-meshheading:7906142-Lysine, pubmed-meshheading:7906142-Magnesium, pubmed-meshheading:7906142-Molecular Sequence Data, pubmed-meshheading:7906142-Molecular Structure, pubmed-meshheading:7906142-Mutagenesis, Site-Directed, pubmed-meshheading:7906142-Streptomyces, pubmed-meshheading:7906142-Structure-Activity Relationship
pubmed:year
1994
pubmed:articleTitle
Role of the divalent metal ion in sugar binding, ring opening, and isomerization by D-xylose isomerase: replacement of a catalytic metal by an amino acid.
pubmed:affiliation
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't