Thymidylate kinase regulation

The enzyme does not appear to be regulated allosterically by nucleotides (3S). Thus, regulatory influence by the kinase on the flow of metabolic traflic through the thymidine phosphates evidently would have to be exerted through changes in its concentration. In the latter connection, it may be relevant that thymidylate kinase is a very unstable activity and that a large portion of the mouse liver enzyme is contained in a latent, inactive form in mitochondria. 

Random oligonucleotide mutagenesis was first applied to promotor sequences that regulate the production of enzymes in cells [21] and was the first method used to alter systematically the functions of enzymes by directed evolution [22], Based on our experience, we will focus on this approach and emphasize recent applications of this methodology to enzymes involved in DNA repair and synthesis, including DNA polymerase enzymes, thymidylate synthase, thymidine kinase, and 06-alkylguanine-DNA alkyltransferase. 

Because of the rapid synthesis of DNA during differentiation, lymphoid cells would be expected to be particularly sensitive to abnormalities in the regulation of the nucleoside pools that serve as precursors for DNA synthesis. The synthesis of thymidine triphosphate is of particular interest because of its specificity for DNA synthesis. The rate limiting step in the de novo pathway to dUMP involves conversion of dUPM to a dTMP by the folate requiring enzyme thymidylate synthetase, vitro incorporation of 3H-thymidine and 3n-deoxyuridine is reduced in bone marrow cultures from folic acid deficient rats (Sakamato and Takaku, 1973). Thymidylate synthetase activity was elevated when assayed in the presence of adequate cofactor (5,10-methylene THF). A salvage pathway also exists for the direct phosphorylation of thymidine by thymidine kinase. This enzyme can exist in two forms (Ellims et al., ... 

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