Isotopic discrimination between 3H and 14C in vitro during enzymatic phosphorylation of labelled thymidine
✍ Scribed by L. Baugnet-Mahieu; R. Goutier; M. Semal
- Publisher
- John Wiley and Sons
- Year
- 1966
- Tongue
- French
- Weight
- 478 KB
- Volume
- 2
- Category
- Article
- ISSN
- 0022-2135
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✦ Synopsis
We compare the phosphorylation of 6-3H-TdR and 2-14C-TdR to TMP, TDP and TTP by tissue extracts and to T M P by purified kiizase pre~aratioiz~. The rate of'pho~phory~ation of'& 3H-TdR is only 0.6 to 0.8 that of 2-14C-TdR. The same isotopic discrimination exists between methyl-labelled thymidines. In mixtures of 3H-TdR and 14C-TdR incubated together with a liver extract, the isotopic ratio is lower in the products than in the substrate. Degradation products of 3H-TdR do not seem to interfere with enzymatic activity. This isotopic discrimination is tentatively ascribed to an isotopic efect of 3H which is mainly detectable at the high substratelenzyme ratios prevailing in the in vitro incubation conditions.