Abstract
Abstract Purine nucleoside phosphorylase (inosine + Pi ⇌ hypoxanthine + α-d-ribose 1-phosphate, EC 2.4.2.1) from Salmonella typhimurium LT-2 has been purified 230-fold. High speed sedimentation equilibrium studies showed that the molecular weight of the native enzyme was 141,000. A molecular weight of 130,000 ± 10% was determined by Sephadex G-150 filtration. Disc gel electrophoresis of the enzyme in the presence of sodium dodecyl sulfate revealed a subunit molecular weight of 23,500, indicating that the enzyme is composed of six subunits. The purified enzyme was found to be specific for the purine ribonucleosides and deoxyribonucleosides, inosine, deoxyinosine, guanosine, deoxyguanosine, adenosine, and deoxyadenosine. The Michaelis constants for inosine, deoxyinosine, and phosphate ion were 50 µm, 47 µm, and 0.37 mm, respectively.
Highlights
High speed sedimentation equilibrium studies showed that the molecular weight of the native enzyme was 141,000
Robertson et al [4] reported that purine nucleoside phosphorylase was induced when wild type S. typhimurium was grown in the presence of any of the six purine nucleosides
The subunit molecular weight of purine nucleoside phosphorylase was estimated from its mobility at various gel concentrations
Summary
Purine nucleoside phosphorylase (inosine + Pi ti hypoxanthine + a-D-ribose l-phosphate, EC 2.4.2.1) from. Salmonella typhimurium LT-2 has been purified 230-fold. High speed sedimentation equilibrium studies showed that the molecular weight of the native enzyme was 141,000. A molecular weight of 130,000 i 10% was determined by Sephadex G-150 filtration. Disc gel electrophoresis of the enzyme in the presence of sodium dodecyl sulfate revealed a subunit molecular weight of 23,500, indicating that the enzyme is composed of six subunits. The purified enzyme was found to be specific for the purine ribonucleosides and deoxyribonucleosides, inosine, deoxyinosine, guanosine, deoxyguanosine, adenosine, and deoxyadenosine. The above findings, a study was undertaken to determine whether only one enzyme was induced in S. typhimurium and if it was capable of catalyzing the phosphorolysis of all six purine nucleosides. This paper reports some of the physical and catalytic properties of the enzyme purified during the investigation
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