title: Adenosine Kinase of T. b. Rhodesiense identified as the putative target of 4-[5-(4-phenoxyphenyl)-2H-pyrazol-3-yl]morpholine using chemical proteomics.
abstract: BACKGROUND
  Human African trypanosomiasis (HAT), a major parasitic disease spread in Africa, urgently needs novel targets and new efficacious chemotherapeutic agents. Recently, we discovered that 4-[5-(4-phenoxyphenyl)-2H-pyrazol-3-yl]morpholine (compound 1) exhibits specific antitrypanosomal activity with an IC(50) of 1.0 microM on Trypanosoma brucei rhodesiense (T. b. rhodesiense), the causative agent of the acute form of HAT.
  
  
  RESULTS
  In this work we show adenosine kinase of T. b. rhodesiense (TbrAK), a key enzyme of the parasite purine salvage pathway which is vital for parasite survival, to be the putative intracellular target of compound 1 using a chemical proteomics approach. This finding was confirmed by RNA interference experiments showing that down-regulation of adenosine kinase counteracts compound 1 activity. Further chemical validation demonstrated that compound 1 interacts specifically and tightly with TbrAK with nanomolar affinity, and in vitro activity measurements showed that compound 1 is an enhancer of TbrAK activity. The subsequent kinetic analysis provided strong evidence that the observed hyperactivation of TbrAK is due to the abolishment of the intrinsic substrate-inhibition.
  
  
  CONCLUSIONS
  The results suggest that TbrAK is the putative target of this compound, and that hyperactivation of TbrAK may represent a novel therapeutic strategy for the development of trypanocides.
authors.affiliation: Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Geneva, Switzerland.
authors.forename: Sabine
authors.initials: S
authors.lastname: Kuettel
authors.forename: Marc
authors.initials: M
authors.lastname: Mosimann
authors.forename: Pascal
authors.initials: P
authors.lastname: Mäser
authors.forename: Marcel
authors.initials: M
authors.lastname: Kaiser
authors.forename: Reto
authors.initials: R
authors.lastname: Brun
authors.forename: Leonardo
authors.initials: L
authors.lastname: Scapozza
authors.forename: Remo
authors.initials: R
authors.lastname: Perozzo
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