title: Metabolism of 4-N-hydroxy-cytidine in Escherichia coli.
abstract: 4-N-hydroxy-cytidine was found to substitute for uridine as a pyrimidine supplement for the growth of Escherichia coli Bu(-). Measurement of the incorporation of 4-N-hydroxy-cytidine-2-(14)C into ribonucleic acid and deoxyribonucleic acid revealed that this compound was converted to cytidine or uridine before utilization. Two pathways for metabolism were considered: (i) the reduction of 4-N-hydroxy-cytidine to cytidine followed by deamination, (ii) the direct hydrolysis of hydroxylamine from 4-N-hydroxy-cytidine to yield uridine. A threefold increase in cytidine (deoxycytidine) deaminase (EC 3.5.4.5) activity, when the cells were grown on 4-N-hydroxy-cytidine, suggested the involvement of this enzyme. More direct proof was obtained by purifying the deaminase 185-fold and finding that it released hydroxylamine from 4-N-hydroxy-cytidine at one-fiftieth the rate at which ammonia was removed from cytidine. This result is consistent with the slower rate of growth of the Bu(-) cells on 4-N-hydroxy-cytidine than cytidine and suggests that the second pathway is the major route for utilization of this compound.
mesh_terms: D000619:Aminohydrolases / Q000302:isolation & purification / Q000378:metabolism; D002247:Carbon Isotopes; D002474:Cell-Free System; D011232:Chemical Precipitation; D002854:Chromatography, Paper; D003470:Culture Media; D003562:Cytidine / Q000378:metabolism*; D004269:DNA, Bacterial / Q000096:biosynthesis; D003641:Deamination; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006898:Hydroxylamines / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism; D012329:RNA, Bacterial / Q000096:biosynthesis; D013053:Spectrophotometry; D014556:Urine / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D003470:Culture Media; D004269:DNA, Bacterial; D006898:Hydroxylamines; D011743:Pyrimidines; D012329:RNA, Bacterial; D003562:Cytidine; D010088:Oxidoreductases; D000619:Aminohydrolases