Nature of inhibition of rat testicular alkaline phosphatase by isatin

Isatin has been found to inhibit rat testicular alkaline phosphatase (EC 3.1.3.1). That the inhibition is non-competitive as well as non-allosteric is evident from a) the hyperbolic curve relating inhibition as a function of inhibitor concentration; b) the small change in enthalpy, free energy and entropy; c) the number of isatin molecules associating with 1 molecule of the enzyme (n=1.29); and, d) the decrease in the values of both Km and Vmax in the presence of isatin.     

An improved procedure for purification of alkaline phosphatase from rat kidney

Riassunto Viene descitto un nuovo metodo per la purificazione della fosfatasi alcalina da rene di ratto. La metodica comprende 4 tappe: (1) isolamento della frazione microsomiale; (2) solubilizzazione dell'enzima dalle strutture microsomiali per mezzo del desossicolato e della lipasi; (3) frazionamento cromatografico su DEAE-Sephadex A-25 ed eluzione con gradiente di concentrazione; (4) ricromatografia delle frazioni attive sullo stesso scambiatore anionico. All'elettroforesi su gel d'amido l'enzima ottenuto si comporta come una proteina omogenea.

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This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche, Impresa Enzimologia.     

Phosphoprotein phosphatase activity of bovine intestinal alkaline phosphatase

The phosphoprotein phosphatase activity of a commercial preparation of bovine intestinal alkaline phosphatase (EC 3.1.3.1) was examined using phosvitin and dentine phosphoprotein as substrates. Over 90% and 70% of the phosphorus from dentine phosphoprotein and phosvitin were hydrolyzed in 2 h. The optimum pH of the enzyme for the dephosphorylation of phosvitin and dentine phosphoprotein was nearly 6. No protein phosphatase activity was observed when the alkaline phosphatases from bovine liver and pulp were investigated.     

Inducing effect of clofibrate on alkaline phosphatase and histidine-glyoxylate aminotransferase in rat liver

Summary The activity of plasma membrane alkaline phosphatase and both mitochondrial and peroxisomal histidineglyoxylate aminotransferase was significantly increased in the livers of male rats following treatment with the hypolipidemic drug clofibrate. Cycloheximide or puromycin administration to rats inhibited the effects of clofibrate.     

Continuous optical determination of alkaline phosphatase

Zusammenfassung Ein kontinuierliches optisches Messverfahren für die Bestimmung der alkalischen Phosphatase mitp-Nitrophenyl-phosphat als Substrat wird ausführlich beschrieben. Das Verfahren wird zur Bestimmung der alkalischen Phosphatase in der Rattenniere angewandt.

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This research is a contribution from the Impresa Enzimologia Group of the Italian Consiglio Nazionale delle Ricerche.     

Differential developmental pattern of acid and alkaline phytase and phosphatase activities in rat intestine

Summary Rat intestine was found to show a distinct acid phytase activity (pH optimum 4.7) in addition to that of an alkaline phytase (pH optimum 8.0). The phytase and phosphatase activities were found to differ in their developmental pattern and responded differentially to some inhibitors. Thus the two activities seem to be due to two independent enzymes and are not the activity of a nonspecific phosphatase as has been suspected formerly.     

Phosphatases IX. Differences in sialic acid content of rat liver alkaline phosphatase isoenzymes

Zusammenfassung Die Heterogeneität der alkalischen Phosphatase in der Rattenleber wird beschrieben. Anodische und kathodische Isoenzyme unterscheiden sich unter anderem durch ihre Reaktion auf die Neuraminidase Behandlung.

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V. Volek, J. tpán, E. Beneová andF. Hemanský, Sb. lék. in print (1973).     

Differential developmental pattern of acid and alkaline phytase and phosphatase activities in rat intestine.

Rat intestine was found to show a distinct acid phytase activity (pH optimum 4.7) in addition to that of an alkaline phytase (pH optimum 8.0). The phytase and phosphatase activities were found to differ in their developmental pattern and responded differentially to some inhibitors. Thus the two activities seem to be due to two independent enzymes and are not the activity of a nonspecific phosphatase as has been suspected formerly.     

Estrogenic inhibition of testicular growth by R2858 in preweanling rats

Daily injections of physiologic doses of R2858 into preweanling rats from the 10th to the 19th day of age resulted in reduced testicular growth compared to controls. Body weights and other organ weights were unaffected. Leydig cells were smaller and less numerous, and showed distinct changes in ultrastructural morphology. Results of this study suggest that alpha-fetoprotein permits normal testicular development during postnatal life.     

Estrogenic inhibition of testicular growth by R2858 in preweanling rats

Summary Daily injections of physiologic doses of R2858 into preweanling rats from the 10th to the 19th day of age resulted in reduced testicular growth compared to controls. Body weights and other organ weights were unaffected. Leydig cells were smaller and less numerous, and showed distinct changes in ultrastructural morphology. Results of this study suggest that -fetoprotein permits normal testicular development during postnatal life.The authors would like to thank Dr Deltour of Roussel UCLAF for the gift of R2858.     

Stimulation of the synthesis and non-competitive inhibition of alkaline phosphatase by theophylline in normal hamster fibroblasts and absence of response in transformed fibroblasts]

Theophylline increases the synthesis of alkaline phosphatase in normal Hamster fibroblasts (activity X6 after 24 hours with theophylline 10-3 M). The enzymatic activity of these cells is inhibited by theophylline in vitro (80% inhibition in the presence of theophylline 10-3 M). The inhibition seems to be non competitive, since the apparent Km of the enzyme is not modified. This stimulator and inhibitor effect of theophylline is absent in Hamster fibroblasts transformed by SV 40 virus.     

Dissociation-constants of metal-ion-complexes with alkaline phosphatase from pig kidney

Summary Using metal-ion buffers it was possible to remove Zn²⁺, Mg²⁺ and Mn²⁺ ions of pig kidney alkaline phosphatase reversibly. The dissociation constants obtained are K_EMg:4·10^–7 M, K_EMn:4·10^–8 M and K_EZn:8·10^–13 M (22°C, pH:9.6, :0.07).Acknowledgement: The authors thank Dr.H. U. Wolf for helpful suggestions and valuable discussion and MissH. Köth for technical assistance.     

Possible role of intestinal alkaline phosphatase activity in thiamine transport

Summary Thiamine deficiency caused a marked decrease of intestinal alkaline phosphatase (al-Pase) activity, but had no effect on the Ca⁺⁺-ATPase activity and Ca⁺⁺-absorption in rats. The al-Pase activity was significantly decreased 1 h after oral administration of ethanol at 0.5 and 2.5 g/kg. In contrast, Mg⁺⁺-, Ca⁺⁺- and (Na⁺+K⁺)-ATPase activities did not change after the administration of ethanol. These findings show that the al-Pase activity, unlike the Ca⁺⁺-ATPase activity, is not related to Ca⁺⁺-absorption. A possible role of al-Pase activity in the active transport of thiamine in the intestine was discussed.     

Partial purification and some characteristics of hamster molar alkaline phosphatase

Summary A rapid 3-step method is given to purify partially hamster molar alkaline phosphatase. Molecular weight was 50,200 and isoelectric point 3.7. The alkaline phosphatases in the mesenchymal and ectodermal parts of the tooth are probably identical.     

Dissociation-constants of metat-ion-complexes with alkaline phosphatase from pig kidney.

Using metal-ion buffers it was possible to remove Zn2+, Mg2+ and Mn2+ ions of pig kidney alkaline phosphatase reversibly. The dissociation constants obtained are KEMg: 4 X 10(-7) M, KEMn: 4 X 10(-8) M and KEZn: 8 X 10(-13) M (22 degrees C, pH: 9.6, mu: 0.07).     

Intracellular localization and heterogeneity of alkaline phosphatase of Yoshida ascites sarcoma

Zusammenfassung In Yoshida-Sarkomzellen ist die alkalische Phosphatase vorwiegend in der partikelfreien Fraktion in gelöster Form lokalisiert. Gelfiltration fÜhrt zu einer Auftrennung des Enzyms im partikelfreien Überstand von 6 Fraktionen, des Enzyms in den Zellkernen bei 2 Fraktionen.

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We are grateful to Tenovus (Wales) for financial support.