nucleotides

DNA is made up of nucleotides, which also make up RNA, coenzymes, and metabolic regulators. Nucleotides consist of a phosphate group, a sugar, and a nitrogenous base. There are five bases, either with one or two nitrogen-containing rings. Nucleotide synthesis occurs through the de novo pathway or the salvage pathway. In de novo synthesis of purines, PRPP converts to PRA, which is then converted to GAR, FGAR, FGAM, AIR, CAIR, SAICAR, AICAR, FACAR, and finally IMP. IMP is further converted to GMP. These nucleotides can be used for RNA, DNA, or energy storage. Up close, DNA is made up of thousands of different nucleotides bound together. Nucleotides also make up RNA, chemical storage molecules, coenzymes, and our metabolic regulators. A nucleotide is an organic molecule made from at least one phosphate group, a pentose sugar, either ribose or deoxyribose, and a nitrogenous base. There are five bases found in nucleotides. These have one nitrogen-containing ring or two. Bases with one are called primidines, bases with two are called purines. Primidines include diene, cytosine, and uracil. Purines include adenine and guanine. There are two pathways of nucleotide synthesis. De novo pathway, where nucleotides are made from scratch using simple molecules such as amino acids, carbon dioxide, and tetrahydrofolate. And the salvage pathway, where free bases and nucleotides are from degraded RNA and DNA are recycled back into nucleotides. This animation will focus on de novo synthesis of purines. Purines are actively synthesized de novo in the liver. First, PRPP converts to PRA by the addition of glutamine amine group, catalyzed by enzyme PRA transferase. PRA converted to GAR in a reaction with glycine and ECP, catalyzed by GAR synthetase. GAR is converted to FGAR when N1O formal tetrahydrofolate donates its formal group, catalyzed by GAR transformolase. FGAR is converted to FGAM when a second glutamine amine is added to FGAR. This is catalyzed by FGAM synthetase. Ring closure occurs, converting FGAM into AIR in an ACP-dependent reaction, catalyzed by AIR synthetase. AIR is carboxylase in the presence of ACP by bicarbonate to form CAIR. This is catalyzed by enzyme AIR carboxylase. L-aspartate is added in an ACP-dependent reaction, forming SAICAR. This is catalyzed by SAICAR synthetase. A fumarate group is cleaved off, producing AICAR. This is catalyzed by adenylsuccinate lease. A fumarate group is cleaved off, producing AICAR. This is catalyzed by adenylsuccinate lease. AICAR is converted to FACAR by the addition of a second N10 formal group. This is catalyzed by enzyme AICAR transformalase. IMP cyclohydrolase closes a second ring, releasing a water molecule and producing IMP. IMP is converted further to GMP by dehydrogenation of IMP by IMP dehydrogenase, forming XMP. Addition of a glutamine-amine group in the presence of water and ACP produces GMP. This is catalyzed by GMP synthetase. Conversion to IMP involves donation of an amino group from aspartate in the presence of GCP to form adenylsuccinate, then elimination of a fumarate group to form IMP. The end products, IMP and GMP, become components of RNA, can be converted into deoxyribonucleotides by ribonucleotide reductase and form DNA, or be converted into energy storage molecules, GTP and ACP.