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  • 1
    Electronic Resource
    Electronic Resource
    Phosphatase activity characterization on the surface of intact bloodstream forms of Trypanosoma brucei (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 220 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Procyclic forms of Trypanosoma brucei possess a phosphatase activity on their external cell surface. This activity, while it dephosphorylates [32P]phosphocasein, is inhibited weakly by NaF and tartrate but strongly by vanadate. In this work, we describe the presence of an external phosphatase activity in intact bloodstream forms of T. brucei. With p-nitrophenyl phosphate (pNPP) as substrate, these intact cells produced 3–5 nmol pNP min−1 mg−1, linearly for up to at least 30 min. The activity was not significantly increased by Mg2+, Mn2+, Ca2+ and Co2+, but was inhibited by vanadate, NaF, p-chloromercuribenzoate and Zn2+ and was insensitive to okadaic acid. Membrane-enriched fractions of parasites contained an acid phosphatase activity, with a pH optimum in the range of 4.5–5.5. This activity hydrolyzed phosphotyrosine (40 nmol phosphate min−1 mg−1) better than phosphothreonine or phosphoserine. Partial purification of this phosphatase yielded a single activity band following gel electrophoresis, a Km value of 0.29 mM with pNPP and was insensitive to the Fe2+/H2O2/ascorbate system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00091-0
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  • 2
    Electronic Resource
    Electronic Resource
    Purification and kinetic properties of a castor bean seed acid phosphatase containing sulfhydryl groups (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 107 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An acid phosphatase (EC 3.1.3.2) has been identified and purified from castor bean (Ricinus communis L., IAC-80) seed through sulphopropyl (SP)-Sephadex, diethylaminoethyl (DEAE)-Sephadex, Sephacryl S-200, and Concanavalin A-Sepharose chromatography. The enzyme was purified 2 000-fold to homogeneity, with a final specific activity of 3.8 μkat mg−1 protein. The purified enzyme revealed a single diffuse band with phosphatase activity on nondenaturing polyacrylamide gel electrophoresis, at pH 8.3. The relative molecular mass, determined by high-performance liquid chromatography (HPLC), was found to be 60 kDa. The acid phosphatase had a pH optimum of 5.5 and an akpparent Km value for p-nitrophenylphosphate of 0.52 mM. The enzyme-catalyzed reaction was inhibited by inorganic phosphate, fluoride, vanadate, molybdate, p-chloromercuribenzoate (pCMB), Cu2+ and Zn2+. The strong inhibition by pCMB, Cu2+ and vanadate suggests the presence of sulfhydryl groups essential for catalysis. The castor bean enzyme also recognized tyrosine-phosphate and inorganic pyrophosphate (KPPi) as substrate. The highest specificity constant (Vmax/Km) was observed with KPPi, making it a potential physiological substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.100201.x
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