BIOCHEMISTRY, BIOMEDICINE & PHARMACEUTICS

Multiple Choice Questions on Purine & Pyrimidine Metabolism Purine metabolism is a crucial biochemical process that involves the biosynthesis, degradation, and recycling of purine nucleotides, which are essential building blocks of DNA and RNA. The de novo biosynthesis of purines requires several enzymes, including glutamine: phosphoribosyl pyrophosphate (PRPP) amidotransferase, which is a committed step and a target for regulation. Other important enzymes involved in purine biosynthesis include adenylosuccinate synthetase and adenylosuccinate lyase. The degradation of purine nucleotides generates uric acid, which is excreted by the kidneys. Dysregulation of purine metabolism can lead to several diseases, including gout and Lesch-Nyhan syndrome. Understanding the complex regulation of purine metabolism is crucial for the development of novel therapeutic strategies. 1. The function of nucleotide includes : a) Second Messenger b) Energy currency and high energy equivalents c...

Pharmacological agents that directly or indirectly inhibit purine and pyrimidine synthesis have been used as anti-bacterial agents and anti-tumor drugs. These classes of drugs inhibit purine / pyrimidine synthesis and availability in the cells thereby decreasing cell replication. The inhibitors of the purine degradation pathway are used for the treatment of Gout. The pharmacological agents / inhibitors are as follows: i) Fluorouracil (anti-tumor agents) ii) Sulfonamides and Trimethoprim (antibacterial agents) iii) Allopurinol (for 'Gout' management) Anti-tumor agents: Fluorouracil is a mechanism-based drug that inhibits the enzyme Thymidylate synthetase (TS). Thymidylate synthetase is an enzyme that catalyzes the synthesis of deoxyuridine monophosphate to deoxythymidine monophosphate, a building block of DNA. The inhibitor of the enzyme led to decreased production of dTMP and reduced substrate for DNA replication and cell cycle.  5-Fluorouracil competes with uracil ...