title: [Regulatory mutants for the synthesis of a 2d purine nucleoside phosphorylase in Escherichia coli K-12. I. Synthesis inducers and the substrate specificity of purine nucleoside phosphorylase in pndR mutants].
abstract: Restoration of the ability to catabolise the purine nucleosides in phenotypic revertants of Escherichia coli K-12 mutants defective in deoD encoded purine nucleoside phosphorylase (PNPase 1) is the result of regulatory pndR mutations for synthesis of a second purine nucleoside phosphorylase (PNPase 2). In pndR+ strains synthesis of PNPase 2 is induced by xanthosine; in pndR mutants catabolising all purine nucleosides synthesis of this enzyme is constitutive; in other pndR mutants only catabolising some of purine nucleosides, this catabolisible nucleosides, namely, deoxyinosine, deoxyadenosine as well as, in some cases, inosine and adenosine, act as inducers of PNPase 2 synthesis. In some pndR mutants with inducible PNPase 2, xanthosine is a stronger inducer, in others it is weaker, in comparison with pndR+ strains. In bacterial cells PNPase 2 catalyses the phosphorolytic cleavage of adenosine, inosine, deoxyinosine, guanosine, deoxyguanosine and xanthosine, though in crude extracts adenosine and deoxyadenosine phosphorylase activities of the enzyme are not expressed.
mesh_terms: D004790:Enzyme Induction / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005796:Genes / Q000187:drug effects; D005798:Genes, Bacterial / Q000187:drug effects; D009154:Mutation; D010430:Pentosyltransferases / Q000096:biosynthesis*; D011684:Purine Nucleosides / Q000378:metabolism; D011683:Purine-Nucleoside Phosphorylase / Q000096:biosynthesis* / Q000235:genetics; D012263:Ribonucleosides / Q000494:pharmacology; D013379:Substrate Specificity / Q000187:drug effects; D014970:Xanthines
chemical_list: D011684:Purine Nucleosides; D012263:Ribonucleosides; D014970:Xanthines; C005893:xanthosine; D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase
vernacular_title: Reguliatornye mutanty po sintezu vtoroĭ purinnukleozidfosforilazy u Escherichia coli K-12. Soobshchenie I. Induktory sinteza i substratnaia spetsifichnost' purinnukleozidfosforilazy u mutantov pndR.