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Thymine Utilization in Escherichia coli K12 on the Role of Deoxyribose l-Phosphate and Thymidine Phosphorylase.

Authors :
Jensen, Kaj Frank
Leer, Johan Chr.
Nygaard, Per
Source :
European Journal of Biochemistry. Dec73 Part 2, Vol. 40 Issue 2, p345-354. 10p. 2 Diagrams, 4 Charts, 4 Graphs.
Publication Year :
1973

Abstract

Exogenously supplied thymine is only poorly utilized by wild-type cells of Escherichia coli for the synthesis of their DNA. It appears that the lack of incorporation of exogenous thymine is due to a lack of endogenous deoxyribosyl groups, which are required for the synthesis of thymidine. Data to be presented in this paper indicate that the ability of different thymine auxotrophs to grow on progressively lower thymine concentrations is a function of their capacity to increase the internal pool of deoxyribose 1-phosphate and/or the level of thymidine phosphorylase. Thymine incorporation in wild-type cells could be observed if the cells possessed an increased deoxyribose 1-phosphate pool. The kinetics of thymine uptake in wild-type cells, in a mutant lacking thymidine phosphorylase and in thymine auxotrophs show that the initial rates of thymine uptake are almost identical and proportional to the external thymine concentration. The experiments in vivo led us to conclude that the incorporation of exogenous thymine occurs via thymidine, which is synthesized from thymine and deoxyribose 1-phosphate, catalyzed by thymidine phosphorylase. In accordance with this studies in vitro with purified thymidine phosphorylase showed that th3Tnidine is synthesized from deoxyribose 1-phosphate and thymine rather than through a deoxyribose transfer from a deoxynucleoside. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00142956
Volume :
40
Issue :
2
Database :
Academic Search Index
Journal :
European Journal of Biochemistry
Publication Type :
Academic Journal
Accession number :
27269884
Full Text :
https://doi.org/10.1111/j.1432-1033.1973.tb03203.x