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Chapter-39 Nucleotides: Chemistry and Metabolism

BOOK TITLE: Textbook of Biochemistry for Medical Students

Author
1. Vasudevan DM
2. S Sreekumari
3. Vaidyanathan Kannan
ISBN
9789350250167
DOI
10.5005/jp/books/11359_39
Edition
6/e
Publishing Year
2011
Pages
12
Author Affiliations
1. Faculty of Medicine, Amrita Vishwa Vidyapeetham, (Amrita University), Kochi, Kerala, Formerly Principal, College of Medicine, Amrita, Kerala; Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, Amrita Vishwa Vidyapeetham (Deemed University), Cochin, Kerala, E-mail: dmvasudevan@aims.amrita.edu, PG Programs and Research College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India, College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India; Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, India
2. Jubilee Mission Medical College, Trissur, Kerala, Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India, Government Medical College, Thrissur and Thiruvananthapuram, Kerala, India; Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India; Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
3. Amrita Institute of Medical Sciences, Kochi, Kerala, India, Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, India, Believers Church Medical College and Hospital, Thiruvalla, Kerala, India
Chapter keywords

Abstract

A nucleotide is composed of a nitrogenous base, a pentose sugar and phosphate groups esterified to the sugar. Purine bases in both DNA and RNA are the same. Purine salvage pathway is mediated by two enzymes: Adenine phosphoribosyl transferase (APRTase) and Hypoxanthine guanine phosphoribosyl transferase (HGPRTase). Committed step of de novo purine synthesis is the reaction catalyzed by amidotransferase. Xanthine oxidase is a metalloflavoprotein containing FAD, molybdenum and iron. Allopurinol inhibits it, which is a good example of ‘suicide inhibition’. End product of purine catabolism is uric acid. Its normal serum level is 3-7 mg/dl. Level is increased in gout. Uric acid crystals deposited in the cooler areas of the body cause tophi. Lesch-Nyhan syndrome is an x-linked inherited disorder of purine metabolism, due to deficiency of HGPRTase. The condition is characterized by self mutilation tendency. Adenosine deaminase deficiency has been treated by gene replacement therapy. In mammalian cells, regulation of pyrimidine synthesis occurs at the level of Carbamoyl phosphate synthase II, which is inhibited by UTP. Deficiency of OMP decarboxylase and OPTase leads to Orotic aciduria.

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