Selenophosphate as a substrate for mammalian selenocysteine synthase, its stability and toxicity
説明
<jats:title>Abstract</jats:title><jats:p>The mechanism of selenocysteine synthesis on tRNA<jats:sup>Sec</jats:sup> in mammals was previously studied by means of HSe<jats:sup>−</jats:sup> as a Se donor to synthesize selenocysteine. It has been recently established that HSe<jats:sup>−</jats:sup> in E. coli is activated by ATP to become selenophosphate (SeP). In this study, we provide evidence that [<jats:sup>75</jats:sup>Se]selenocysteine is produced by bovine selenocysteine synthase from Ser‐tRNA<jats:sup>Sec</jats:sup> and [<jats:sup>75</jats:sup>Se]SeP, synthesized from elemental <jats:sup>75</jats:sup>Se and Tris(trimethylsilyl)phosphite. We also studied the stability of SeP by NMR measurement. SeP was stable during storage under nitrogen at ‐80°C for 3 months in 0.2 M Hepes buffer at pH 6.8. However, SeP decomposed at 0°C in air (half life 32 hrs) or at 22°C under nitrogen (half life 30 hrs) at pH 6.8. The half lives of SeP at ‐19°C in air and at 0°C under nitrogen at pH 6.8 were 740 and 840 hrs, respectively. At pH 4 under nitrogen at 22°C, the half life was 240 hrs. The half life was only 9.2 hrs at pH 9 under nitrogen at 0°C. Thus, SeP was proved to be stable at low temperature, under acidic and anaerobic conditions, but labile under neutral and alkaline conditions.The LD<jats:sub>50</jats:sub> of SeP administered i.p. to mice was 37.5 mg/kg body weight.</jats:p>
収録刊行物
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- BioFactors
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BioFactors 9 (1), 27-36, 1999-01
Wiley
