Figure 1.

Hexokinase (HK) catalyzes the conversion of [³H]UTP to [³H]UDP. (A) Time course for ATP and UTP hydrolysis in the presence of 1 unit/ml HK. Incubations were carried out at 37°C in 1 ml Hepes-buffered DMEM (pH 7.4) containing 25 mM glucose and 1 mM (0.5 μCi) of either [³H]ATP or [³H]UTP. At the times indicated, 5 mM EDTA was added to the samples followed by boiling. (B) Time course for the conversion of [³H]UTP to [³H]UDP in the presence of 10 units/ml HK. Incubations were as indicated above except for the HK concentration. The [³H]species were resolved by HPLC as detailed. The results are expressed as the percent conversion of [³H]nucleotide triphosphate to [³H]nucleotide diphosphate. Data indicate the mean value of one experiment representative of two independent experiments performed with duplicate samples that differed by less than 20%.