Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other, nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD+ and NADH (H for hydrogen), respectively.
In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. Ribonucleotides themselves are basic monomeric building blocks for RNA. Deoxyribonucleotides, formed by reducing ribonucleotides with the enzyme ribonucleotide reductase (RNR), are essential building blocks for DNA. There are several differences between DNA deoxyribonucleotides and RNA ribonucleotides. Successive nucleotides are linked together via phosphodiester bonds.
A salvage pathway is a pathway in which a biological product is produced from intermediates in the degradative pathway of its own or a similar substance. The term often refers to nucleotide salvage in particular, in which nucleotides are synthesized from intermediates in their degradative pathway.
Phosphoribosyl pyrophosphate (PRPP) is a pentose phosphate. It is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, as well as in pyrimidine nucleotide formation. Hence it is a building block for DNA and RNA. The vitamins thiamine and cobalamin, and the amino acid tryptophan also contain fragments derived from PRPP. It is formed from ribose 5-phosphate (R5P) by the enzyme ribose-phosphate diphosphokinase:
Phosphoribosylformylglycinamidine cyclo-ligase is the fifth enzyme in the de novo synthesis of purine nucleotides. It catalyzes the reaction to form 5-aminoimidazole ribotide (AIR) from formylglycinamidine-ribonucleotide FGAM. This reaction closes the ring and produces a 5-membered imidazole ring of the purine nucleus (AIR):
In molecular biology, the protein domain SAICAR synthase is an enzyme which catalyses a reaction to create SAICAR. In enzymology, this enzyme is also known as phosphoribosylaminoimidazolesuccinocarboxamide synthase. It is an enzyme that catalyzes the chemical reaction
In enzymology, a nucleotide diphosphatase (EC 3.6.1.9) is an enzyme that catalyzes the chemical reaction
In enzymology, a NMN nucleosidase (EC 3.2.2.14) is an enzyme that catalyzes the chemical reaction
In enzymology, an anthranilate phosphoribosyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, an ATP phosphoribosyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a dioxotetrahydropyrimidine phosphoribosyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a nicotinate-nucleotide-dimethylbenzimidazole phosphoribosyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a nicotinate phosphoribosyltransferase (EC 6.3.4.21) is an enzyme that catalyzes the chemical reaction
In enzymology, a xanthine phosphoribosyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a FMN adenylyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a glucose-1-phosphate adenylyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a glucuronate-1-phosphate uridylyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, nicotinamide-nucleotide adenylyltransferase (NMNAT) (EC 2.7.7.1) are enzymes that catalyzes the chemical reaction
In enzymology, a nicotinate-nucleotide adenylyltransferase (EC 2.7.7.18) is an enzyme that catalyzes the chemical reaction
Decaprenyl-phosphate phosphoribosyltransferase is an enzyme with systematic name trans,octacis-decaprenylphospho-beta-D-ribofuranose 5-phosphate:diphosphate phospho-alpha-D-ribosyltransferase. This enzyme catalyses the following chemical reaction
