From the Research
Glycine is the amino acid that is required for purine nucleotide synthesis but not used as a precursor in pyrimidine nucleotide synthesis. In purine synthesis, glycine contributes its entire molecule to form the purine ring structure, specifically providing carbon 4, carbon 5, and nitrogen 7 of the purine ring. This incorporation occurs during the early steps of purine synthesis when glycine condenses with phosphoribosyl pyrophosphate (PRPP) derivatives.
Key Points
- The role of glycine in purine synthesis is well-established, with studies such as 1 highlighting the importance of glycine and serine in fueling purine nucleotide biosynthesis in human lung cancer tissues.
- In contrast, pyrimidine synthesis primarily relies on aspartate and carbamoyl phosphate (derived from glutamine) as nitrogen and carbon sources, with no direct incorporation of glycine, as discussed in 2 and 3.
- The other amino acids listed—aspartate, glutamine, and carbamoyl phosphate (derived from glutamine)—are involved in pyrimidine synthesis, while serine and arginine are not directly incorporated into either purine or pyrimidine rings as major precursors in the same manner as glycine is for purines.
Evidence Summary
The most recent and highest quality study, 1, published in 2019, provides insight into the de novo synthesis of serine and glycine in human lung cancer tissues, supporting the critical role of glycine in purine nucleotide synthesis. While other studies, such as 2 and 3, discuss the roles of glutamine and aspartate in pyrimidine synthesis, they do not alter the conclusion that glycine is specifically required for purine nucleotide synthesis and not used in pyrimidine nucleotide synthesis.