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This sqadia.com medical video lecture provides detail of metabolism of pyrimidines. This lecture talks about materials and enzymes required for synthesis of pyrimidines. All the steps involved in the biosynthesis of pyrimidine are comprehensively elaborated. Moreover, light is shed on synthesis of pyrimidine nucleotides. Later on, catabolism of cytosine, uracil, and thymine is also considered.
The term prototrophic is used for mammals and most of the lower vertebrates that can synthesize purines and pyrimidines. This section is about pyrimidines which is a heterocyclic ring. Materials required for synthesis of pyrimidines are also discussed here along with various enzymes required for processing. Moreover, a comparative elaboration is also given about differences in purine and pyrimidine synthesis.
Biosynthesis of Pyrimidine
Synthesis of carbamoyl phosphate is the first step in the synthesis of pyrimidine. After that formation of carbamoyl aspartic acid takes place which then leads to the formation of dihydro-orotic acid. Then enzyme dihydro-orotate dehydrogenase catalyzes the formation of orotic acid. To know about the details and complete steps leading to the formation of pyrimidine, stream this medical v-learning lecture on sqadia.com.
Synthesis of Pyrimidine Nucleotides
UMP is phosphorylated by ATP to form UDP. UDP is further phosphorylated by ATP to form UTP. Subsequently, CTP can be synthesized from UTP. Following this, formation of deoxyuridine diphosphate takes place by enzyme ribonucleoside reductase. Discussion continues on how synthesis of thymine deoxyribonucleotides takes place. Conclusively, comments are given on synthesis of pyrimidine deoxyribonucleotides.
Catabolism of Pyrimidines
The first step in the catabolism of cytosine and uracil is the dephosphorylation to nucleosides by 5’-nucleotidases. Uracil is reduced to 5,6-dihydrouracil which upon hydrolysis produces β-ureidopropionic acid. β-ureidopropionic acid then forms CO2, NH3 and β-alanine. Next subject of discussion is thymine which is released from thymidine. It is produced by deamination of 5-methylcytosine.