title: [Substrate specifity in Amoeba proteus].
abstract: Three different phosphatases ("slow", "middle" and "fast") were found in Amoeba proteus (strain B) after PAGE and a subsequent gel staining in 1-naphthyl phosphate containing incubation mixture (pH 9.0). Substrate specificity of these phosphatases was determined in supernatants of homogenates using inhibitors of phosphatase activity. All phosphatases showed a broad substrate specificity. Of 10 tested compounds, p-nitrophenyl phosphate was a preferable substrate for all 3 phosphatases. All phosphatases were able to hydrolyse bis-p-nitrophenyl phosphate and, hence, displayed phosphodiesterase activity. All phosphatases hydrolysed O-phospho-L-tyrosine to a greater or lesser degree. Only little differences in substrate specificity of phosphatases were noticed: 1) "fast" and "middle" phosphatases hydrolysed naphthyl phosphates and O-phospho-L-tyrosine less efficiently than did "slow" phosphatase; 2) "fast" and "middle" phosphatases hydrolysed 2- naphthyl phosphate to a lesser degree than 1-naphthyl phosphate 3) "fast" and "middle" phosphatases hydrolysed O-phospho-L-serine and O-phospho-L-threonine with lower intensity as compared with "slow" phosphatase; 4) as distinct from "middle" and "slow" phosphatases, the "fast" phosphatase hydrolysed glucose-6-phosphate very poorly. The revealed broad substrate specificity of "slow" phosphatase together with data of inhibitory analysis and results of experiments with reactivation of this phosphatase by Zn2+-ions after its inactivation by EDTA strongly suggest that only the "slow" phosphatase is a true alkaline phosphatase (EC 3.1.3.1). The alkaline phosphatase of A. proteus is secreted into culture medium where its activity is low. The enzyme displays both phosphomono- and phosphodiesterase activities, in addition to supposed protein phosphatase activity. It still remains unknown, to which particular phosphatase class the amoeban "middle" and "fast" phosphatases (pH 9.0) may be assigned.
authors.forename: V A
authors.initials: VA
authors.lastname: Sopina
mesh_terms: D000656:Amoeba / Q000201:enzymology*; D000818:Animals; D017077:Culture Media, Conditioned / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D010744:Phosphoric Monoester Hydrolases / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D015800:Protozoan Proteins; D010744:Phosphoric Monoester Hydrolases