Inhibition of deoxythymidine kinase by beryllium

Abstract Deoxythymidine kinase, partially purified from 24 hr regenerating rat liver, is markedly inhibited by BeSO 4 . The inhibition is competitive with the cofactor, magnesium. The 50 per cent inhibitory level of BeSO 4 was 2.2 mM when 2.5 mM MgCl 2 was included in the assay system. The K m for magnesium-enzyme was 7.5 × 10 −4 M; the K i was 9.5 × 10 −5 M.