title: Cytidine deaminase activity in Penicillium politans NRC-510.
abstract: Cell-free extracts of nitrate-grown Penicillium politans NRC-510 catalyzes the hydrolytic deamination of cytidine to uridine. Uridine was chromatographically identified in cell-free extracts. The enzyme exhibited optimum pH and temperature activities at 6.5 and 80 degrees C respectively. Thermal stability experiments indicated that the enzyme restored its activity at 80 degrees C for at least 60 minutes. When cell-free extracts were incubated at 90 degrees C for 5 minutes enzyme activity was inhibited by about 33%. The involvement of sulfhydryl group(s) in the catalytic site of the enzyme was shown. HgCl2 (5 x 10(-3) M) and CuSO4 (10(-2) M) caused a complete inhibition of enzyme activity. Ethylene diamine tetraacetate at a concentration of 5 x 10(-3) M and 10(-2) M inhibited the enzyme as well. Whereas, MgCl2, CoSO2 and MnCl2 had a remarkable activating effect. Dialysis of the cell-free extracts resulted to an increase in enzyme activity by about 30%. To our knowledge the thermophilic nature of the cytidine deaminase of P. politans NRC-510 is unique.
authors.affiliation: Department of Microbial Chemistry, National Research Centre, El-Tahrir Street, Dokki, Cairo, Egypt. alielshafei@yahoo.com
authors.forename: Ali M
authors.initials: AM
authors.lastname: Elshafei
authors.forename: Nadia H
authors.initials: NH
authors.lastname: Ali
authors.forename: Latifa A
authors.initials: LA
authors.lastname: Mohamed
mesh_terms: D002712:Chlorides / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D019327:Copper Sulfate / Q000494:pharmacology; D003470:Culture Media; D003564:Cytidine Deaminase / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride / Q000494:pharmacology; D017895:Manganese Compounds / Q000494:pharmacology; D008627:Mercuric Chloride / Q000494:pharmacology; D009566:Nitrates; D010407:Penicillium / Q000201:enzymology* / Q000254:growth & development; D013696:Temperature; D014529:Uridine / Q000378:metabolism
chemical_list: D002712:Chlorides; D003470:Culture Media; D017895:Manganese Compounds; D009566:Nitrates; D015636:Magnesium Chloride; D003035:Cobalt; D008627:Mercuric Chloride; D003564:Cytidine Deaminase; C026305:cobalt sulfate; D019327:Copper Sulfate; C025340:manganese chloride; D014529:Uridine