Pyrimidine metabolism
This article includes a list of general references, but it lacks sufficient corresponding inline citations. (August 2008) |
Pyrimidine biosynthesis occurs both in the body and through organic synthesis.[1]
De novo biosynthesis of pyrimidine
Steps | Enzymes | Products | |
1 | carbamoyl phosphate synthetase II[2] |
carbamoyl phosphate | This is the regulated step in the pyrimidine biosynthesis in animals. |
2 | aspartic transcarbamoylase ( aspartate carbamoyl transferase)[2] |
carbamoyl aspartic acid | The phosphate group is replaced with Aspartate. This is the regulated step in the pyrimidine biosynthesis in bacteria. |
3 | dihydroorotase[2] | dihydroorotate |
Ring formation and Dehydration. |
4 | dihydroorotate dehydrogenase[3] (the only mitochondrial enzyme) | orotate |
Dihydroorotate then enters the mitochondria where it is oxidized through removal of hydrogens. This is the only mitochondrial step in nucleotide rings biosynthesis.
|
5 | orotate phosphoribosyltransferase[4] | OMP |
PRPP donates a Ribose group.
|
6 | OMP decarboxylase[4] |
UMP | Decarboxylation |
uridine-cytidine kinase 2[5] | UDP | Phosphorylation. ATP is used. | |
nucleoside diphosphate kinase |
UTP |
Phosphorylation. ATP is used. | |
CTP synthase |
CTP |
Glutamine and ATP are used. |
De Novo biosynthesis of a
In other organisms (
Pyrimidine catabolism
β-aminoisobutyrate acts as a rough indicator for rate of DNA turnover.[8]
Regulations of pyrimidine nucleotide biosynthesis
Through negative feedback inhibition, the end-products UTP and UDP prevent the enzyme CAD from catalyzing the reaction in animals. Conversely, PRPP and ATP act as positive effectors that enhance the enzyme's activity.[9]
Pharmacotherapy
Modulating the pyrimidine metabolism pharmacologically has therapeutical uses, and could implement in cancer treatment.[10]
Pyrimidine synthesis inhibitors are used in active moderate to severe rheumatoid arthritis and psoriatic arthritis, as well as in multiple sclerosis. Examples include Leflunomide and Teriflunomide (the active metabolite of leflunomide).
Prebiotic synthesis of pyrimidine nucleotides
In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions. The RNA world hypothesis holds that in the primordial soup there existed free-floating pyrimidine and purine ribonucleotides, the fundamental molecules that combine in series to form RNA. Complex molecules such as RNA must have emerged from relatively small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of pyrimidine and purine nucleotides, both of which are necessary for reliable information transfer, and thus natural selection and Darwinian evolution. Becker et al. showed how pyrimidine nucleosides can be synthesized from small molecules and ribose, driven solely by wet-dry cycles.[11]
References
- PMC 9326563.
- ^ a b c "Entrez Gene: CAD carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase".
- ^ "Entrez Gene: DHODH dihydroorotate dehydrogenase".
- ^ a b "Entrez Gene: UMPS uridine monophosphate synthetase".
- ^ "Entrez Gene: UCK2 uridine-cytidine kinase 2".
- PMID 28115257.
- PMID 26059768.
- PMID 4363656.
- PMID 6105839.
- PMC 9326563.
- ^ Becker S, Feldmann J, Wiedemann S, Okamura H, Schneider C, Iwan K, Crisp A, Rossa M, Amatov T, Carell T. Unified prebiotically plausible synthesis of pyrimidine and purine RNA ribonucleotides. Science. 2019 Oct 4;366(6461):76-82. doi: 10.1126/science.aax2747. PMID 31604305
External links
- Overview at Queen Mary, University of London