SUMMARY: The synthesis of the pyrimidine biosynthetic enzymes is repressed by the pyrimidine nucleotide end-products of the pathway. However, purine nucleotides also play a role. In this study, I have measured expression of the genes () in strains harbouring mutations that permit manipulation of the intracellular pools of both pyrimidine and purine nucleotides. The results identify the effectory purine compound as being a guanine nucleotide; it is probably GTP, but it may be GDP or GMP. The synthesis of carbamoylphosphate synthase, encoded by and particularly dihydroorotase, encoded by and dihydroorotate dehydrogenase, encoded by is stimulated by the guanine nucleotide, while the synthesis of aspartate transcarbamoylase, encoded by and orotate phosphoribosyltransferase, encoded by is inhibited by guanine nucleotides. The regulatory pattern of each gene is discussed in relation to present knowledge on gene structure and regulatory mechanism.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error