purinas

Purines are a class of nitrogen-containing heterocyclic compounds formed by fusion of a pyrimidine ring with an imidazole ring. The purine bases adenine and guanine are essential components of DNA and RNA; adenine pairs with thymine in DNA and with uracil in RNA, and guanine pairs with cytosine. Purine nucleotides such as ATP and GTP, and coenzymes like NAD, FAD, and cyclic nucleotides, arise from or contain this scaffold. The fused ring system gives purines distinctive hydrogen-bonding and stacking properties that support nucleic acid structure and protein interactions.

Purines participate in multiple cellular roles beyond nucleic acids, including energy transfer, signal transduction, and metabolism. They appear as monomers in ATP, GTP, cAMP, cGMP, and as adenosine-containing cofactors such as NAD and FAD, as well as in CoA-related structures. Availability is tightly regulated to maintain nucleotide pools for transcription, replication, and signaling.

Purine biosynthesis occurs via de novo synthesis and salvage. De novo synthesis builds the purine ring on ribose-5-phosphate from starting substrates such as glycine, glutamine, aspartate, formyl groups, and CO2, using one-carbon transfers from folate cofactors. Salvage pathways recycle free purines—hypoxanthine and guanine—into nucleotides via HGPRT. This balance maintains nucleotide pools required for cellular processes.

Purine catabolism in humans ends with uric acid, produced by xanthine oxidase and excreted by the kidneys. Humans lack uricase, contributing to higher uric acid levels and sometimes gout. Dietary sources include meat and seafood, while endogenous synthesis is a major contributor. Purine metabolism intersects many areas of biochemistry, underpinning genetic information storage, energy transfer, and signaling.