Degradation of [3H]thymidine by a pentosyltransferase (EC 2.4.2.4) in the plasma of man and different animals

Abstract
[3H]Thymidine is degraded by an enzyme (thymidine phosphorylase; EC 2.4.2.4) which we have identified in the plasma of man and some animals. The presence of this enzyme in plasma or sera used to supplement culture media may, under certain experimental conditions, limit the validity of measuring the uptake of radiolabeled thymidine as a means of defining DNA synthesis.