title: Characteristics of cytidine aminohydrolase activity in Trypanosoma cruzi and Crithidia fasciculata.
abstract: Cytidine deaminase (cytidine aminohydrolase, 3.5.4.5) is present in Crithidia fasciculata (a mosquito parasite) and in Trypanosoma cruzi (a human pathogen). The enzyme from C. fasciculata deaminated both cytidine and deoxycytidine, the affinity for the former being much lower than the latter. Affinities for both substrates are equal for the T. cruzi enzyme. The production of the enzyme in C. fasciculata was significantly stimulated by the addition of a number of pyrimidine nucleosides (cytidine, uridine, 5-bromouridine, thymidine, orotidine) to the culture media. Only cytidine stimulated enzyme production in T. cruzi. The enzyme from both organisms was unstable in air, even in the frozen state. Stabilization was achieved under anaerobic conditions.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D003421:Crithidia / Q000201:enzymology*; D003562:Cytidine / Q000378:metabolism / Q000494:pharmacology; D003564:Cytidine Deaminase / Q000378:metabolism*; D003841:Deoxycytidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D009700:Nucleoside Deaminases / Q000378:metabolism*; D011741:Pyrimidine Nucleosides / Q000494:pharmacology; D013379:Substrate Specificity; D014349:Trypanosoma cruzi / Q000201:enzymology*
chemical_list: D011741:Pyrimidine Nucleosides; D003841:Deoxycytidine; D003562:Cytidine; D009700:Nucleoside Deaminases; D003564:Cytidine Deaminase