Adenosine kinase from Cryptosporidium parvum

Jon Galazka, Boris Striepen, Buddy Ullman

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Analysis of the Cryptosporidium parvum genome demonstrates that the parasite cannot synthesize purines de novo and reveals that the sole route for purine salvage by the parasite is via adenosine kinase (CpAK). In order to initiate a biochemical characterization of CpAK and ultimately validate this apparently essential enzyme as a therapeutic target, the CpAK gene was redesigned for optimum codon usage, overexpressed in Escherichia coli, and the recombinant protein purified to homogeneity and characterized. CpAK appears to be specific for adenosine among the naturally occurring nucleosides but can utilize ATP, GTP, UTP and CTP as the phosphate donor. The enzyme exhibits Km values of 1.4 μM for adenosine and 41 μM for ATP, has a pH optimum ∼7.0, and is dependent upon the presence of a divalent cation. Structure-activity data intimate that catalysis requires contacts between residues on CpAK with the six-position of the purine ring and the O2′ and O3′ hydroxyls of the ribose sugar. Additionally, 4-nitro-6-benzylthioinosine, a compound that demonstrates therapeutic promise against the related parasite Toxoplasma gondii, also inhibits adenosine phosphorylation by CpAK. The overproduction and purification of CpAK now enables a thorough evaluation of its potential as a drug target.

Original languageEnglish (US)
Pages (from-to)223-230
Number of pages8
JournalMolecular and Biochemical Parasitology
Volume149
Issue number2
DOIs
StatePublished - Oct 2006

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Adenosine Kinase
Cryptosporidium parvum
Adenosine
Parasites
Adenosine Triphosphate
Cytidine Triphosphate
Purines
Uridine Triphosphate
Ribose
Escherichia coli Proteins
Divalent Cations
Toxoplasma
Enzymes
Guanosine Triphosphate
Catalysis
Nucleosides
Recombinant Proteins
Codon
Hydroxyl Radical
Phosphates

Keywords

  • Adenosine kinase
  • Cryptosporidium parvum
  • Parasite
  • Protozoa
  • Purine salvage

ASJC Scopus subject areas

  • Molecular Biology
  • Parasitology

Cite this

Adenosine kinase from Cryptosporidium parvum. / Galazka, Jon; Striepen, Boris; Ullman, Buddy.

In: Molecular and Biochemical Parasitology, Vol. 149, No. 2, 10.2006, p. 223-230.

Research output: Contribution to journalArticle

Galazka, Jon ; Striepen, Boris ; Ullman, Buddy. / Adenosine kinase from Cryptosporidium parvum. In: Molecular and Biochemical Parasitology. 2006 ; Vol. 149, No. 2. pp. 223-230.
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