Monoselenophosphate: Its Hydrolysis and Its Ability to Phosphorylate Alcohols and Amines

The rate of hydrolysis of monoselenophosphate, the labile selenium donor compound required for the synthesis of selenium-dependent enzymes and seleno-tRNAs, was determined by31P NMR spectroscopy. The rate depended on the pH of the solution and was maximal at a pH ∼7. This suggests that the dianion is the species that reacts fastest. Added alcohols and amines do not significantly affect the rate of hydrolysis but are phosphorylated. The entropy of activation is positive for the hydrolysis of monoselenophosphate. These data suggest a dissociative in nature mechanism for the hydrolysis of monoselenophosphate involving a monomeric metaphosphate-like transition state in the rate-determining step.