title: [Flavinogenesis and regulation of purine biosynthesis de novo in Pichia guilliermondi mutants resiatant to 8-azaguanine].
abstract: 93 mutants resistant to 8-azaguanine (AGR-mutants) were derived from the strain of Pichia guilliermondii with blocked guanine deaminase (EC 3.5.4.3.) by UV-irradiation. The mutants retained the ability to uptake 8-azaguanine and guanine but could not deaminate guanine. Some of the AGR-mutants were found to accumulate large amounts of hypoxanthine and small amounts of guanine in the cultural medium. The inhibitory effect of guanine and 8-azaguanine but not adenine on the purine biosynthesis de novo was considerably decreased. It was established observing the rates of 5 amino 4-imidazoleribotide accumulation in purine-requiring AGR-mutants in the presence of different purines. The regulation of the activity and biosynthesis of IMP-dehydrogenase (EC 1. 2. 1. 14) with guanine compounds in AGR-mutants was completely preserved. Under cultivating in iron-rich medium all the AGR-mutants accumulated more riboflavin than the strain H-101 and the wild type strain. That occured as a result of the increase of flavinogenesis velocity in AGR-mutants during late logarithmic and negative growth acceleration phases. Some of mutants also synthesized more riboflavin in iron-deficient medium. Depression of riboflavine synthetase was not observed in the iron-rich cells of AGR-mutants.
mesh_terms: D001203:Ascomycota / Q000378:metabolism*; D001375:Azaguanine / Q000494:pharmacology*; D006147:Guanine / Q000096:biosynthesis; D007042:Hypoxanthines / Q000096:biosynthesis; D007168:IMP Dehydrogenase / Q000378:metabolism; D007501:Iron / Q000494:pharmacology; D009154:Mutation; D010843:Pichia / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011687:Purines / Q000096:biosynthesis*; D012256:Riboflavin / Q000096:biosynthesis*
chemical_list: D007042:Hypoxanthines; D011687:Purines; D006147:Guanine; D007501:Iron; D007168:IMP Dehydrogenase; D001375:Azaguanine; D012256:Riboflavin
vernacular_title: Osobennosti flavinogeneza i reguliatsii biosinteza purinov de novo u mutantov drozhzheĭ Pichia guilliermondii, rezistentnykh k 8-azaguaninu