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Nishiyama, T., Kawamura, Y., Kawamoto, K., Matsumura, H., Yamamoto, N., Ito, T., Ohyama A., Katsuragi, T. and Sakai, T. (1985) Antineoplastic effects in rats of 5-fluorocytosine in combination with cytosine deaminase capsules. Cancer Research, 45, 1753-176.

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• TITLE: Purification and characterization of Aspergillus parasiticus cytosine deaminase for possible deployment in suicide gene therapy

  AUTHORS: Hassan Zanna, A. J. Nok, S. Ibrahim, H. M. Inuwa

  KEYWORDS: Cytosine Deaminase; Cytosine, 5-Fluorocytosine; Aspergillus parasiticus; Activation Energy

  JOURNAL NAME: Advances in Biological Chemistry, Vol.2 No.2, May 10, 2012

  ABSTRACT: Cytosine Deaminase (CD) from Aspergillus parasiticus was purified and characterized. Time course for maximal CD production (50 μmol/min/mg) was at 72 hrs. The enzyme was purified 387.73 folds with an overall yield of 13%. The CD had pH optimum of 7.2, a temperature optimum of 40℃ - 45℃, activation of energy (Ea) of 8.4 KJ/mol and a t1/2 of 1.10 hr. A. parasiticus CD stoichiometrically deaminated Cyto-sine and 5-fluorocytosine (5-FC) with the KM values of 0.19mM and 0.30 mM respectively. Studies on the effect of pH on KM and Vmax gave pKa1 of 5.8 and pKa2 of 6.3 with enthalpy of ionization of 43.01 KJ/mole suggesting histidine in the active site. The enzyme was strongly inhibited by Ca2+, Co2+, Zn2+ and Hg2+ and completely inhibited by Cu2+ and Fe2+ at 50 mM. Therefore, A. parasiticus CD can be compared with CDs from other sources that are used in suicide gene therapy.