Linked Life Data

18066911

Source:http://linkedlifedata.com/resource/pubmed/id/18066911

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6-7
pubmed:dateCreated
2007-12-10
pubmed:abstractText
Interactions of trimeric calf spleen purine nucleoside phosphorylase (PNP) with guanine (Gua) and its analogue, 9-deazaguanine (9-deaza-Gua), were studied by means of the steady-state fluorescence. The aim was to test the hypothesis that the enzyme stabilizes the anionic form of purine, inferred previously from the unusual increase of fluorescence observed after binding of guanine by calf spleen PNP. We have found that the dissociation constants obtained form titration experiments are in fact pH-independent in the range 7.0-10.25 for both PNP/Gua and PNP/9-deaza-Gua complexes. In particular, at pH 7.0 we found Kd = 0.12 +/- 0.02 micro M for Gua and 0.16 +/- 0.01 micro M for 9-deaza-Gua, while at the conditions where there is more than 40% of the anionic form the respective values were Kd = 0.15 +/- 0.01 micro M for Gua (pH 9.0) and 0.25 +/- 0.02 micro M for 9-deaza-Gua (pH 10.25). Hence, the enzyme does not prefer binding of anionic forms of these ligands in respect to the neutral ones. This result questions the involvement of the anionic forms in the reaction catalyzed by trimeric PNPs, and contradicts the hypothesis of a strong hydrogen bond formation between the enzyme Asn 243 residue and the purine N7 position.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
1525-7770
pubmed:author
pubmed:issnType
Print
pubmed:volume
26
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
841-7
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Fluorescence studies of calf spleen purine nucleoside phosphorylase (PNP) complexes with guanine and 9-deazaguanine.
pubmed:affiliation
Department of Biophysics, Institute of Experimental Physics, Warsaw University, Warsaw, Poland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't