Haloperoxidases are enzymes capable of formation of carbon^halogen bonds in the presence of hydrogen peroxide and halide ions. A mechanism of halogenation catalyzed by heme-and metal-independent bacterial haloperoxidases di¡ers from other representatives of this group of enzymes. Here we report for the ¢rst time that bacterial non-heme haloperoxidases possess a phosphatase activity. Chloroperoxidase from Serratia marcescens W 250 puri¢ed up to homogeneity is shown to catalyze p-nitrophenylphosphate hydrolysis (K m value, 1.8 þ 0.1 mM at pH 5.7). The reaction is activated by Mg 2+ and F 3 , and is inhibited by WO 4 23 , tartrate, acetate and phosphate anions. The irreversible inhibition by phenylmethanesulfonyl £uoride, modi¢cator of serine residue in active site, decreases in the presence of phosphate ions. A mechanism of phosphoesters hydrolysis by non-heme haloperoxidases is proposed. ß

Selenophosphate synthetase (SPS) catalyses formation of the universal donor of selenium equivalents in a living cell. It performs the selenophosphate formation from ATP and selenide in ATP-dependent manner. We have checked a catalytically inactive mutant C17S of bacterial SPS from E.coli, E197D, for ATP hydrolysis and ATP-binding. The ratio obtained for ATP-binding is 9.52 nM ATP: 7.0 nmol enzyme, however, the fraction of the protein applied to the size-exclusive column TSK 2000 under reaction conditions was homogenious. It is likely under the ATP-binding conditions C17S mutant of SPS represents a monomer. A sequence alignment of bacterial mutant C17S from strain K12 with a human SEPHSI shows it exhibits of 31% homology. It is supposingly SPSI is a functional and structural analogue of C17S and has a similar biological activity.