Linked Life Data

8611497

Source:http://linkedlifedata.com/resource/pubmed/id/8611497

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
16
pubmed:dateCreated
1996-6-6
pubmed:databankReference
pubmed:abstractText
UDP-galactose 4-epimerase is one of three enzymes in the metabolic pathway that converts galactose into glucose1-phosphate. Specifically this enzyme catalyzes the interconversion of UDP-galactose and UDP-glucose. The molecular structure of the NADH/UDP-glucose abortive complex of the enzyme from Escherichia coli has been determined by X-ray diffraction analysis to a nominal resolution of 1.8 A and refined to an R-factor of 18.2% for all measurement X-ray data. The nicotinamide ring of the dinucleotide adopts the syn conformation in relationship to the ribose. Both the NADH and UDP-glucose are in the proper orientation for a B-side specific transfer from C4 of the sugar to C4 of the dinucleotide. Those residues implicated in glucose binding include Ser 124, tyr 149, Asn 179, Asn199, Arg 231, and Tyr 299. An amino acid sequence alignment of various prokaryotic and eukaryotic epimerases reveals a high degree of conservation with respect to those residues involved in both NADH and substrate binding. The nonstereospecificity displayed by epimerase was originally thought to occur through a simple rotation about the bond between the glycosyl C1 oxygen of the 4-ketose intermediate and the beta-phosphorous of the UDP moiety, thereby allowing the opposite side of the sugar to face the NADH. The present structure reveals that additional rotations about the phosphate backbone of UDP are necessary. Furthermore, the abortive complex model described here suggests that Ser 124 and Tyr 149 are likely to play important roles in the catalytic mechanism of the enzyme.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
23
pubmed:volume
35
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5137-44
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
Molecular structure of the NADH/UDP-glucose abortive complex of UDP-galactose 4-epimerase from Escherichia coli: implications for the catalytic mechanism.
pubmed:affiliation
Institute for Enzyme Research, Graduate School, University of Wisconsin, Madison 53705, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.