Inhibition of deoxythymidine kinase by beryllium

Deoxythymidine kinase, partially purified from 24 hr regenerating rat liver, is markedly inhibited by BeSO4. The inhibition is competitive with the cofactor, magnesium. The 50 per cent inhibitory level of BeSO4 was 2.2 mM when 2.5 mM MgCl2 was included in the assay system. The Km for magnesium-enzyme was 7.5 × 10−4 M; the Ki was 9.5 × 10−5 M.