BIOSYNTHESIS OF PYRIMIDINES.pptx

BIOSYNTHESIS OF PYRIMIDINES.pptx

• 1.
  BIOSYNTHESIS OF PYRIMIDINES INTRODUCTION: • Pyrimidine is an aromatic heterocyclic organic compound. It has two nitrogen atoms at position 1 and 3 in the ring. • In nuclei acids, three types of nucleobases are pyrimidine derivatives – SOURCE : PRESENTED BY: PRASHANT VC DEPT OF ZOOLOGY GUK
• 2.
  BIOSYNTHESIS : • Thebiosynthesis of pyrimidines is a simpler process than purines. • There are two pathways leading to pyrimidine synthesis: SALVAGE PATHWAY – the synthesis of nucleotides by recycle the free bases or nucleosides released from nuclei acid breakdown. DE NOVO PATHWAY – the synthesis of nucleotides begin with their metabolic precursors : amino acids, ribose-5-phosphate, carbon dioxide and one-carbon units. • Pyrimidine synthesis is a de novo synthesis pathway involving six steps reactions. • The six members pyrimidine ring is made first and then attached to ribose-5- monophosphate. • This pathway results in the synthesis of Uridine-5-monophosphate (UMP). • Out of 6 enzymes involved in this pathway, 5 are present in the cytosol and 1 is present on the outer surface of inner mitochondrial membrane.
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  DE NOVO SYNTHESISOF UMP : STEP 1 : synthesis of carbamoyl phosphate STEP 2 : synthesis of carbamoyl aspartate STEP 3 : ring closure and dihydroorotate formation STEP 4 : oxidation of dihydroorotate STEP 5 : acquisition of the ribose phosphate moiety STEP 6 : decarboxylation to form UMP
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  SYNTHESIS OF OTHERPYRIMIDINE NUCLEOTIDES : The UMP thus formed is converted to UDP by an ATP-dependent kinas reaction. UDP serves as a precursor for the synthesis of dUMP, dTMP, UTP AND CTP. Ribonucleotide reductase converts UDP to dUDP, by a thioredoxin-dependent reaction. From N^5 ,N^10-methylene tetrahydrofolate methyl group is transferred to form deoxythymidine monophosphate. UDP produce UTP and then cytidine triphosphate is synthesized from UTP by amination.
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  IMPORTANCE: • Essential buildingblocks of nucleic acids • Biologically very important heterocycles • Used in anti-biotics , used as anti-bacterical and anti-fungal also • Derivative of pyrimidine also possess good anti-viral properties REFERENCE : • Lehninger_Principles_of_BIOCHEMISTRY 6th edition • Textbook of biochemistry: U. Satyanarayana U. Chakrapani • www.ncbi.nlm.nih.gov • www.boundless.com/textbooks