Purine Metabolism PDF

purine metabolism Dr. Yasmin Mohammed Marei Ass. Professor of Medical Biochemistry and Molecular Biology  Biosynthesis of purines a. De novo synthesis : biochemical pathway where purines are formed from different metabolic intermediates b. Salvage system: it is the conversion...

purine metabolism Dr. Yasmin Mohammed Marei Ass. Professor of Medical Biochemistry and Molecular Biology  Biosynthesis of purines a. De novo synthesis : biochemical pathway where purines are formed from different metabolic intermediates b. Salvage system: it is the conversion of free purines or purine nucleosides to corresponding nucleotides directly  De novo synthesis of purine  Every cell can form its own purine except the brain, RBCS and lymphocytes.  The sources of purine’s atoms are: Steps of purine de novo synthesis Purine de novo synthesis Regulation of purine synthesis  Purine salvage pathway  It is important to supply purine nucleotides to the cells that can’t undergo the de novo synthesis. There are 2 systems for purine salvage  salvage of free purines  salvage of purine nucleotides 1- salvage of free purines 2- salvage of purine nucleotides  Adenosine → AMP  by adenosine kinase enzyme  Deoxy Adenosine → dAMP  by Deoxy adenosine kinase enzyme Lesch–Nyhan syndrome (LNS)  rare inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT).  Catabolism of purines  Adenosine is deaminated to inosine and then hydrolysed to hypoxanthine  Guanosine is converted to xanthine.  Then, hypoxanthine and xanthine are oxidized into uric acid by xanthine oxidase.  Uric acid is the end product of purine catabolism. Catabolism of purines Metabolism of purines Rate limiting step in de novo synthesis of purine is a. Synthesis of PRPP b. Synthesis of AMP c. Synthesis of IMP d. Synthesis of ribose- 5 phosphate The end product of purine catabolism is a. Guanine b. Xanthine c. Hypoxanthine d. Uric acid