In most cases these amino acids can be synthesize by one step reactions from central metabolites. They are simple in structure and their synthesis is also straight forward.
Notice that each pathway begins with a central metabolite or something derived from "central metabolism". Using common compounds instead of synthesizing them from scratch saves energy and conserves genes since fewer enzymes are needed to code for the pathways.
nucleotide; biosynthesis; purine; pyrimidine; multifunctional protein
Eriksson S and Wang L (2008) Molecular mechanisms of mitochondrial DNA depletion diseases caused by deficiencies in enzymes in purine and pyrimidine metabolism. Nucleosides, Nucleotides & Nucleic Acids 27: 800–808.
Pyrimidine nucleotide synthesis with cofactor recycling
Traut TW (1988) Enzymes of nucleotide metabolism: the significance of subunit size and polymer size for biological function and regulatory properties. CRC Critical Reviews of Biochemistry 23: 121–169.
Implementation of the Enzymatic Synthesis
Traut TW and Jones ME (1996) Uracil metabolism – UMP synthesis from orotic acid or uridine and conversion of uracil to β‐alanine: enzymes and cDNAs. Progress in Nucleic Acid Research and Molecular Biology 53: 1–77.
Purine and Pyrimidine Nucleotide Synthesis and …
Stevens RC and Lipscomb WN (1992) A molecular mechanism for pyrimidine and purine nucleotide control of aspartate transcarbamylase. Proceedings of the National Academy of Sciences of the USA 89: 5281–5285.
eters of purified enzymes involved in nucleotide synthesis
Nygaard P (1983) Utilization of preformed purine bases and nucleosides. In: Munch‐Petersen A (ed.) Metabolism in Nucleotides, Nucleosides and Nucleobases in Microorganisms, pp. 27–93. London: Academic Press.
Purine and Pyrimidine Nucleotide Synthesis and Metabolism 17 of 20
The biosynthesis of serine and glycine constitute a major metabolic pathway that plays a central role in the formation of other amino acids, nucleic acids and phospholipids. When is grown on glucose, fully 15% of carbon assimilated passes through the serine pathway. Synthesis of serine and glycine starts with oxidation of 3-phosphoglycerate forming 3-phosphohydroxy pyruvate and NADH. A transamination reaction with glutamate forms 3-phosphoserine and removal of the phosphate yields serine. Glycine is generated by removal of the methyl group from serine. Energy is not required for this pathway, in fact it yields energy in the form of reduced NADH.
Regulation of Purine Nucleotide Synthesis
Instead of uric acid secretion, guanine and IMP can be used for recycling purposes and nucleic acid synthesis in the presence of PRPP and aspartate (NH3 donor).