MONOSELENOPHOSPHATE - SYNTHESIS, CHARACTERIZATION, AND IDENTITY WITH THE PROKARYOTIC BIOLOGICAL SELENIUM DONOR, COMPOUND SEPX

A labile, selenium donor compound required for synthesis of selenium-d ependent enzymes and seleno-tRNAs is formed from ATP and selenide by t he SELD enzyme. This compound, tentatively identified as a selenophosp hate [Veres, Z., Tsai, L., Scholz, T. D., Politino, M., Balaban, R. S. , & Stadtman, T. C. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 2975-2979 ], is indistinguishable from chemically prepared monoselenophosphate b y P-31 NMR spectroscopy and ion pairing HPLC. Furthermore, addition of chemically prepared monoselenophosphate caused a dose-dependent decre ase in the amount of Se-75 incorporated into tRNAs from (SePX)-Se-75 g enerated in situ by SELD enzyme. A procedure is described for the chem ical synthesis of monoselenophosphate in which the readily prepared (M eO)3PSe is converted in quantitative yield to (TMSO)3PSe followed by c omplete cleavage of the latter to monoselenophosphate in oxygen-free a queous buffer. The chemical properties of chemically synthesized monos elenophosphate are described.