Incorporation and Degradation of C and H-labeled Thymidine by Sugarcane Cells in Suspension Culture.

Sugarcane cells growing in suspension culture degrade exogenous thymidine, releasing thymine. Thymine is not utilized for DNA synthesis. Thymine is rapidly catabolized to beta-aminoisobutyric acid which is found within the cell. Thymidine in the medium is used for DNA synthesis. The label of [2-(14)C]thymidine is lost as (14)CO(2), but the label of [(3)H]methylthymidine is found in the cell as [(3)H]beta-aminoisobutyric acid, some of which is used for the synthesis of other cell components. The degradation of thymidine can be partially inhibited by addition of certain substituted pyrimidines.