Sgarrella, Francesco and Frassetto, Luciano and Allegrini, Simone and Camici, Marcella and Carta, Maria Caterina and Fadda, Paola and Tozzi, Maria Grazia and Ipata, Piero Luigi (2007) Characterization of the adenine nucleoside specific phosphorylase of Bacillus cereus. Biochimica et Biophysica Acta. General Subjects, Vol. 1770 (10), p. 1498-1505. ISSN 0304-4165. eISSN 1872-8006. Article.
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Adenosine phosphorylase, a purine nucleoside phosphorylase endowed with high specificity for adenine nucleosides, was purified 117-fold from vegetative forms of Bacillus cereus. The purification procedure included ammonium sulphate fractionation, pH 4 treatment, ion exchange chromatography on DEAE-Sephacel, gel filtration on Sephacryl S-300 HR and affinity chromatography on N6-adenosyl agarose. The enzyme shows a good stability to both temperature and pH. It appears to be a homohexamer of 164±5 kDa. Kinetic characterization confirmed the specificity of this phosphorylase for 6-aminopurine nucleosides. Adenosine was the preferred substrate for nucleoside phosphorolysis (kcat/Km 2.1 × 106 s−1 M−1), followed by 2′-deoxyadenosine (kcat/Km 4.2 × 105 s−1 M−1). Apparently, the low specificity of adenosine phosphorylase towards 6-oxopurine nucleosides is due to a slow catalytic rate rather than to poor substrate binding.
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