. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) BIOSYNTHESIS OF NUCLEOSIDES AND NUCIEOTIDES 259 OH point of ottock of urid^J tronsferose HOCH2 point of otlock of gli/cosy/ tronsferose Uridyl Fig. I. Uridyl-Phospho-1-Glucose (UDPG). TPN will dehydrogenate the latter ester (Warburg, Christian and Griese^^) the rate of liberation of glucose ester can be followed in the ultraviolet range at 340 m/x by reduction of TPN (Warburg, Christian and Griese^^) . ^^P labelled inorganic pyroph
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) BIOSYNTHESIS OF NUCLEOSIDES AND NUCIEOTIDES 259 OH point of ottock of urid^J tronsferose HOCH2 point of otlock of gli/cosy/ tronsferose Uridyl Fig. I. Uridyl-Phospho-1-Glucose (UDPG). TPN will dehydrogenate the latter ester (Warburg, Christian and Griese^^) the rate of liberation of glucose ester can be followed in the ultraviolet range at 340 m/x by reduction of TPN (Warburg, Christian and Griese^^) . ^^P labelled inorganic pyrophos- phate was utilized in the reaction and for each mol radioactive pyrophosphate used one mol a-glucose-i-phosphate was liberated. If the cleavage took place at arrow number i (Fig. i) the resulting nucleotide should be uridine triphos- phate (UTP). It is possible to isolate the radioactive ester by barium precipita- tion, by chromatography through a column of Dowex CI", by paper-iono- phoresis and by paper chromatogra- phy (ethanol-ammonium acetate pH , (Paladini and Leloir^^). In all these procedures the isolated nucleotide behaves like a di- or tri-phosphate. In the chroma- Cs^o togram (see Fig. 2) it appears more charged than uridine diphosphate (UDP), moving, more slowly. Since it has one mol ^^P-pyro- phosphate per mol uracil it seems evident that it is UTP and a chemical analysis confirmed this. UTP seems to act slowly as a phosphoryl donor in the hexokinase test^^; interestingly enough, if a small amount of adenosine diphosphate (ADP) is present this reaction goes much f aster^^. UDP is not active in this test, which is a very sensitive assay for nucleoside triphosphates. It is of particular interest, however, to describe the enzymic reaction in which UTP plays the role of a uridyl donor. This is in the" back reaction" of thepyrophosphorol- ysis, UTP plus a-glucose-i-phosphate in the presence of Zwischenferment gives - test PS JO [ control UTP UD
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