Pyrimidine Biosynthesis and Degradation (Catabolism)

Pyrimidines are structural components in many natural compounds, such as nucleotides, nucleic acids, vitamins, pterins, and antibiotics. In all organisms, pyrimidine nucleotides serve essential functions in nucleic acids as well as in cell metabolism, such as the activation of sugars for polysaccharide and phospholipid synthesis as well as glycosylation of proteins and lipids. In mammals, pyrimidines are crucial to the glucuronidation in detoxification reactions in the liver. Pyrimidine nucleotides have been shown to be involved in many extracellular processes, such as in modulating the tone of vascular smooth muscle and in functioning as neurotransmitter and neuromodulators in the central, peripheral, and enteric nervous system. The size of the pyrimidine nucleotide pools in cells is determined by the relative contributions of de novo synthesis and the interconversion reactions, together with salvage and presence or absence of enzymes of catabolic degradation. Some inherited disorders of pyrimidine biosynthesis and degradation have been diagnosed. Synthetic pyrimidine analogs act as antimetabolites; by selective interference in metabolic pathways and RNA and DNA synthesis, these and synthetic or natural enzyme inhibitors can combat infection, virus, tumor, and autoimmune diseases.