[Identification and some properties of cattle splenocyte nucleus phosphoprotein phosphatase activatorin various tissues]. / Identifikatsiia v razlichnykh tkaniakh i nekotorye svoistva aktivatora fosfoproteinfosfatazy kletochnykh iader selezenki byka.

An activator of phosphoprotein phosphatase from bovine spleen cell nuclei has been isolated from different tissues (rat liver, bovine liver, spleen and kidney). The activator increases the enzyme activity by a factor of 4-5. The activator is heat-stable (it withstands incubation at 95 degrees C for 10 min) but loses its activity by 50% in 6-7 hrs at 4 degrees C.

[Distribution and biotransformation of labelled pantothenate in cytoplasmic and mitochondrial fractions of the rat liver with a deficiency of pantothenic acid]. / Raspredelenie i biotransformatsiia mechenogo pantotenata v tsitoplazmaticheskoi i mitokhondrial'noi fraktsii pecheni krys s nedostatochnost'iu pantotenovoi kisloty.

Experiments were conducted on white rats given synthetic rations devoid of pantothenic acid during 10 weeks. Intensification of 14C-pantothenate deposition was recorded 30 min and 4 h after its intraperitoneal administration. The mitochondrial fraction of the liver accumulated the isotope in time. High-performance liquid chromatography used for separation of the vitamin labeled metabolites has revealed phosphopantothenate (pantothenate), phosphopantothein, CoA and dephospho-CoA (pantetein) in the liver homogenate, while in the mitochondria extracts only CoA and dephospho-CoA (pantetein) were detected. It has been suggested that dephosphorylation of pantothenate metabolites and rapid transformation of phosphopantetein into CoA may take place during the separation of the fractions.

[Phosphoprotein phosphatase nonspecifically hydrolyzes CoA]. / Fosfoproteinfosfataza nespetsificheski gidrolizuet CoA.

CoA hydrolysis was studied by a homogenous phosphoprotein phosphatase (EC 3.1 3.16) preparation from bovine spleen nuclei at pH 5.8. Phosphoprotein phosphatase catalyzed hydrolysis of the CoA 3'-phosphoester bond to form dephospho-CoA and Pi. The Km value for phosphoprotein phosphatase with CoA as substrate was 3.7 mM, the specific activity - 0.26 mmol Pi.min-1.mg-1. Phosphoprotein phosphatase did not essentially catalyze the calcium pantothenate hydrolysis (not more than 2% as compared with the CoA hydrolysis rate).

[Phosphoprotein phosphatases from cell nuclei of the bovine spleen: physico-chemical properties]. / Fosfoproteinfosfataza kletochnykh iader selezenki byka: fiziko-khimicheskie svoistva.

The physico-chemical properties of phosphoprotein phosphatase (EC 1.3.1.16) from bovine spleen cell nuclei were investigated. The enzyme was shown to possess a wide substrate specificity and to catalyze dephosphorylation of phosphocasein, ATP, ADP and p-nitrophenylphosphate (pNPP). The Km values for ATP, ADP and pNPP are 0.44, 0.43 and 1.25 mM, respectively. The molecular weight of the enzyme as determined by gel filtration on Sephadex G-75 and electrophoresis in polyacrylamide gel of different concentrations is approximately 33 000. SDS-polyacrylamide gel electrophoresis revealed two protein bands with Mr 12 000 and 18 000. The enzyme molecule predominantly contains acidic amino acid residues, two free SH-groups and two disulphide bonds. Phosphoprotein phosphatase is a glycoprotein with the carbohydrate content of about 22%, and has an additional absorption maximum at 560 nm. The enzyme is competitively inhibited by ammonium molybdate (Ki = 0.37 microM) and non-competitively by sodium fluoride (Ki = 1.3 mM). Incubation of phosphoprotein phosphatase with 2 mM phenylmethylsulfonylfluoride (PMSF) for 25 hours resulted in a approximately 46% loss of the enzyme activity. Ammonium molybdate, sodium fluoride and PMSF reversibly inhibit the enzyme. Modification of aminoacid SH-groups, NH2-groups and histidine led to a decrease of the enzyme activity. Incubation of phosphoprotein phosphatase with [gamma-33P]ATP resulted in the incorporation of 0.33 mol of 33P per mol of the enzyme. The mechanism of the enzyme-catalyzed hydrolysis of the phosphoester bond is discussed.