Linked Life Data

12173924

Source:http://linkedlifedata.com/resource/pubmed/id/12173924

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
33
pubmed:dateCreated
2002-8-13
pubmed:abstractText
Trichomonas vaginalis is a parasitic protozoan and the causative agent of trichomoniasis. Its primary purine salvage system, consisting of a purine nucleoside phosphorylase (PNP) and a purine nucleoside kinase, presents potential targets for designing selective inhibitors as antitrichomonial drugs because of lack of de novo synthesis of purine nucleotides in this organism. cDNA encoding T. vaginalis PNP was isolated by complementation of an Escherichia coli strain deficient in PNP and expressed, and the recombinant enzyme was purified to apparent homogeneity. It bears only 28% sequence identity with that of human PNP but 57% identity with the E. coli enzyme. Gel filtration showed the enzyme in a hexameric form, similar to the bacterial PNPs. Steady-state kinetic analysis of T. vaginalis PNP-catalyzed reactions gave K(m)'s of 31.5, 59.7, and 6.1 microM for inosine, guanosine, and adenosine in the nucleosidase reaction and 45.6, 35.9, and 12.3 microM for hypoxanthine, guanine, and adenine in the direction of nucleoside synthesis. This substrate specificity appears to be similar to that of bacterial PNPs. The catalytic efficiency of this enzyme with adenine as substrate is 58-fold higher than that with either hypoxanthine or guanine, representing a distinct disparity with the mammalian PNPs, which have negligible activity with either adenine or adenosine. The kinetic mechanism of T. vaginalis PNP-catalyzed reactions, determined by product inhibition and equilibrium isotope exchange, was by random binding of substrates (purine base and ribose 1-phosphate) with ordered release of the purine nucleoside first, followed by inorganic phosphate. Formycin A, an analogue of adenosine known as an inhibitor of E. coli PNP without any effect on mammalian PNPs, was shown to inhibit T. vaginalis PNP with a K(is) of 2.3 microM by competing with adenosine. T. vaginalis PNP thus belongs to the family of bacterial PNPs and constitutes a target for antitrichomonial chemotherapy.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
41
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
10382-9
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:12173924-Adenine, pubmed-meshheading:12173924-Adenosine, pubmed-meshheading:12173924-Amino Acid Sequence, pubmed-meshheading:12173924-Animals, pubmed-meshheading:12173924-Bacterial Proteins, pubmed-meshheading:12173924-Binding, Competitive, pubmed-meshheading:12173924-Catalysis, pubmed-meshheading:12173924-DNA, Complementary, pubmed-meshheading:12173924-Enzyme Inhibitors, pubmed-meshheading:12173924-Escherichia coli, pubmed-meshheading:12173924-Formycins, pubmed-meshheading:12173924-Kinetics, pubmed-meshheading:12173924-Molecular Sequence Data, pubmed-meshheading:12173924-Protozoan Proteins, pubmed-meshheading:12173924-Purine-Nucleoside Phosphorylase, pubmed-meshheading:12173924-Recombinant Proteins, pubmed-meshheading:12173924-Sequence Alignment, pubmed-meshheading:12173924-Sequence Analysis, Protein, pubmed-meshheading:12173924-Sequence Homology, Amino Acid, pubmed-meshheading:12173924-Substrate Specificity, pubmed-meshheading:12173924-Trichomonas vaginalis
pubmed:year
2002
pubmed:articleTitle
The purine nucleoside phosphorylase from Trichomonas vaginalis is a homologue of the bacterial enzyme.
pubmed:affiliation
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143-0446, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.