title: Hydrolysis of dihydrouridine and related compounds.
abstract: Dihydrouridine is absent from the tRNA of almost all hyperthermophiles and most Archaea but is ubiquitous in the tRNA of Eubacteria and Eukaryotes. In order to investigate whether this could be due to instability, the rate of ring opening of dihydrouridine was measured between 25 and 120 degrees C. The dihydrouridine ring is stable at 25 degrees C, but the half-life at 100 degrees C and pH 7 is 9.1 h, which is comparable to the doubling time of hyperthermophiles. This suggests an explanation for the absence of dihydrouridine from the tRNA of hyperthermophiles. The rates of ring opening of dihydrouracil, dihydrothymine, and 1-N-methyldihydrouracil were measured at 100 degrees C and pH 6-9, as were the equilibrium constants for ring closure of the ureido acids to the dihydrouracils. The pH rate profiles for ring opening and ring closing were calculated from the data. Possible roles for dihydrouracils in the pre-RNA world are discussed.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093-0506, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: House
authors.forename: S L
authors.initials: SL
authors.lastname: Miller
mesh_terms: D001105:Archaea; D001419:Bacteria; D005057:Eukaryotic Cells; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008433:Mathematics; D012343:RNA, Transfer / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014529:Uridine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry*
chemical_list: C010922:5,6-dihydrouridine; D012343:RNA, Transfer; D014529:Uridine