Salvage pathway
Encyclopedia
A salvage pathway is a pathway
in which nucleotide
s (purine
and pyrimidine
) are synthesized from intermediates in the degradative pathway for nucleotides.
Salvage pathways are used to recover bases
and nucleosides that are formed during degradation
of RNA
and DNA
. This is important in some organs because some tissues cannot undergo de novo synthesis
.
The salvaged bases and nucleosides can then be converted back into nucleotides.
can then phosphorylate this compound to deoxythymidine diphosphate and triphosphate.
or PRPP) to bases, creating nucleotide monophosphates. There are two types of phosphoribosyltransferases: adenosine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Lesch-Nyhan syndrome
is associated with a deficiency of HGPRT.
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...
in which nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s (purine
Purine
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
and pyrimidine
Pyrimidine
Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring...
) are synthesized from intermediates in the degradative pathway for nucleotides.
Salvage pathways are used to recover bases
Bases
Bases may refer to:*Bases , a military style of dress adopted by the chivalry of the sixteenth century.*Business Association of Stanford Entrepreneurial Students...
and nucleosides that are formed during degradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...
of RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
and DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. This is important in some organs because some tissues cannot undergo de novo synthesis
De novo synthesis
De novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to their being recycled after partial degradation. For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as...
.
The salvaged bases and nucleosides can then be converted back into nucleotides.
Pyrimidines
Uridine phosphorylase adds ribose-1-phospate to the free base uracil, forming uridine monophosphate. Uridine kinase then phosphorylates this nucleoside into its diphosphate and triphosphate forms. Deoxythymidine phosphorylase adds deoxyribose-1-phosphate to thymine, forming deoxythymidine monophosphate. Thymidine kinaseThymidine kinase
Thymidine kinase is an enzyme, a phosphotransferase : 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase, . It can be found in most living cells. It is present in two forms in mammalian cells, TK1 and TK2...
can then phosphorylate this compound to deoxythymidine diphosphate and triphosphate.
Purines
Phosphoribosyltransferases add activated ribose-5-phosphate (called phosphoribosyl pyrophosphatePhosphoribosyl pyrophosphate
Phosphoribosyl pyrophosphate is a pentosephosphate.It is formed from ribose 5-phosphate by the enzyme ribose-phosphate diphosphokinase.It plays a role in transferring phospho-ribose groups in several reactions:...
or PRPP) to bases, creating nucleotide monophosphates. There are two types of phosphoribosyltransferases: adenosine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Lesch-Nyhan syndrome
Lesch-Nyhan syndrome
Lesch–Nyhan syndrome , also known as Nyhan's syndrome, Kelley-Seegmiller syndrome and Juvenile gout, is a rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase , produced by mutations in the HPRT gene located on X chromosome. LNS affects about...
is associated with a deficiency of HGPRT.
| Nucleoside | Enzyme | Nucleotide >- | hypoxanthine Hypoxanthine Hypoxanthine is a naturally occurring purine derivative. It is occasionally found as a constituent of nucleic acids where it is present in the anticodon of tRNA in the form of its nucleoside inosine. It has a tautomer known as 6-Hydroxypurine. Hypoxanthine is a necessary additive in certain cell,... |
hypoxanthine/guanine phosphoribosyl transferase (HGPRT) | >- | hypoxanthine/guanine phosphoribosyl transferase (HGPRT) | GMP Guanosine monophosphate Guanosine monophosphate, also known as 5'-guanidylic acid or guanylic acid and abbreviated GMP, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase... >- | adenine Adenine Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA... |
adenine phosphoribosyltransferase Adenine phosphoribosyltransferase Adenine phosphoribosyltransferase is an enzyme that in humans is encoded by the APRT gene.- Function :APRTase is an enzyme involved in the purine nucleotide salvage pathway... (APRT) |
AMP Adenosine monophosphate Adenosine monophosphate , also known as 5'-adenylic acid, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid and the nucleoside adenosine. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine... |
External links
- "Enzymes in the methionine salvage pathway: structure and function" at Brandeis UniversityBrandeis UniversityBrandeis University is an American private research university with a liberal arts focus. It is located in the southwestern corner of Waltham, Massachusetts, nine miles west of Boston. The University has an enrollment of approximately 3,200 undergraduate and 2,100 graduate students. In 2011, it...