Nonparticipation of Ribonucleic Acid in Glutathionc and Ophthalmic Acid Synthesis

FIG. 2. Ultraviolet absorption spectra of 5.ribosyluracil diphosnhate glucose.The spectra were obtained with the Cary model 14 recording spectrophotometer.The pH was adjusted from 7 to 13 and 14 bv the addition of 10 N NaOH to the samule and to the blank.Corrections for resulting dilutions of 0.9% at pH 13 and 9% at pH 14 were not made.With the use of a crude preparation of galactose-1-P uridyl transferase (13), a galactose-1-P dependent release of glucose-l-P from # UDP-glucose was demonstrated.This reaction was followed by observing TPN reduction in the presence of glucose-6-P dehydrogenase and phosphoglucomutase.Approximately 1 mole of TPN was reduced per mole of fi UDP-glucose added.The zero order rate constant with 1// TJDP-glucose was approximately 16% of that for UDP-glucose with similar concentrations.The presence of $ UDP-galactose pyrophosphorylase activity could also be demonstrated in crude brewers' yeast extract.This was shown by the formation of $ UDP-galactose from + UTP and galactose-1-P.The question of whether there exists one or separate enzymes which catalyze 5ribosyluracil and uridine nucleotide reactions is at present unanswered.This problem and the problem of whether these compounds can act as glycosyl donors are under active investigation.