Catabolism of nucleotides.biochemistry.pptx

Catabolism

1. Catabolism of nucleotides

2. A: Catabolism of purines

3. Degradation of uric acid into various products in different animal species

4. B: Catabolism of pyrimidines The pathway of pyrimidines degradation generally leads to ammonium ion and then to urea synthesis. Step 1: CMP , UMP and deoxyIMP is converted into Cytidine, Uridine deoxythymidine . This reaction is catalyzed by the enzyme Nucleotidase . Step 2: Cytidine is deaminated into Uridine. This reaction is catalyzed by “Cytidine deaminase”. Step 3: Uridine and deoxy thymidine (in case of DNA) is converted into Uracine and Thymidine. This reaction is catalyzed by Uridine phosphorylase. Here on inorganic phosphate is substituted on the first carbon of hydrolyzed Glycosidic linkage sugar molecule. The sugar molecule is released as in the form of Ribose-1-Phosphate and deoxy Ribose-1-Phosphate . Step 4: Uracil and thymine is converted into dihydroUracil and dihydroThymine . This reaction is catalyzed by DihydroUracil and dihydroThymine dehydrogenase. In this reaction one NADPH is oxidized into NADP+. Step 5: DihydroUracil and dihydroThymine is converted into β- Ureido Propionate and β- ureido isobutyrate . This reaction is catalyzed by dihydropyrimidinase . In this reaction the cyclized molecule is converted into linear by cleaving the covalent bond at particular place . Step 6: β- Urido propionate and β- ureido isobutyrate is converted into β- alanine and β- amino isobutyrate . This reaction is catalyzed by β- Ureido Propionase . The secondary products of this reaction are Ammonium ion (NH4+) and Carbon dioxide.

5. The β- alanine and β- amino Isobutyrate is converted into Malonic semialdehyde and Methyl malonic semialdehyde by transamination process. This reaction is catalyzed by amino transferase and secondary substrate is α- ketoglutarate and secondary product is Glutamine. Malonic semialdehyde and methyl malonic semialdehyde is converted into Malonyl~coA . These two products are entering in the part of Fatty acid catabolism like methyl malonyl Patheway .