Pyrimidine Metabolism in Rat Brain Cortex and Liver
Pyrimidine nucleotide synthesis proceeds via a salvage pathway and a de novo pathway. In rat liver all enzymes involved in UMP synthesis from bicarbonate have a considerable activity (1–4), but in rat brain not all enzymes of the OA-pathway (orotic acid) have been demonstrated, although a significant incorporation of [14C]bicarbonate into OA was found (5). A considerable activity of uridine kinase is present in brain (6,7). OA and uracil can not pass the blood-brain barrier (8), but uridine can be taken up (9). In this study we compare the de novo and salvage pathways by measuring the incorporation of aspartate into OA and assaying the activities of DHOdehydrogenase (dihydroorotic acid dehydrogenase), OPRT (orotic acid phosphoribosyltransferase), ODC (orotidylate decarboxylase), uridine kinase and uridine phosphorylase.
KeywordsBrain Cortex Salvage Pathway Orotic Acid Considerable Activity Pyrimidine Nucleotide
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