User:Natalie Van Ochten/Sandbox 1
From Proteopedia
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==Active Site== | ==Active Site== | ||
| - | The normal DDAH regulation mechanism depends on the presence of Cys249 in the active site that acts as a nucleophile in the mechanism | + | The normal DDAH regulation mechanism depends on the presence of Cys249 in the active site that acts as a nucleophile in the mechanism <ref name="stone"[doi:10.1021/bi052595m]</ref>. The Cys249 is used to attack the guanidinium carbon on the substrate that is held in the active site via hydrogen bonds. This is followed by collapsing the tetrahedral product to get rid of the alkylamine leaving group. A thiouronium intermediate is then formed with sp2 hybridization. This intermediate is hydrolyzed to form citrulline. The His162 protonates the leaving group in this reaction and generates hydroxide to hydrolyze the intermediate formed in the reaction. Studies suggest that Cys249 is neutral until binding of guanidinium near Cys249 decreases Cys249’s pKa and deprotonates the thiolate to activate the nucleophile. Other studies suggest that the Cys249 and an active site Histidine162 form an ion pair to deprotonate the thiolate. Cys249 and His162 can also form a binding site for inhibitors to bind to which stabilizes the thiolate. This is important in regulating NO activity in organisms and designing drugs to inhibit this enzyme <ref name="stone" />. |
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==Different Isoforms== | ==Different Isoforms== | ||
| - | DDAH has two main isoforms | + | DDAH has two main isoforms <ref name="frey" />. DDAH-1 colocalizes with nNOS (neuronal NOS). This enzyme is found mainly in the brain and kidney of organisms <ref name="tran" />. DDAH-2 is found in tissues with eNOS (endothelial NOS) <ref name="frey" />. DDAH-2 localization has been found in the heart, kidney, and placenta <ref name="tran" />. Additionally, studies show that DDAH-2 is expressed in iNOS containing immune tissues (inducible NOS) <ref name="frey" />. Both of the isoforms have conserved residues that are involved in the catalytic mechanism of DDAH (Cys, Asp, and His). The differences between the isoforms is in the substrate binding residues and the lid region residues. DDAH-1 has a positively charged lid region while DDAH-2 has negatively charged lid. In total, three salt bridge differ between DDAH-1 and DDAH-2 isoforms. Researchers can take advantage of the fact that there are two different isoforms of this enzyme and create drugs that target one isoform over another to control NO levels in specific tissues in the body <ref name="frey" />. |
This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes. | This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes. | ||
Revision as of 12:04, 28 March 2017
Dimethylarginine Dimethylaminohydrolase
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References
Tran CTL, Leiper JM, Vallance P. The DDAH/ADMA/NOS pathway. Atherosclerosis Supplements. 2003 Dec;4(4):33-40. PMID:14664901 doi:10.1016/S1567-5688(03)00032-1
Frey D, Braun O, Briand C, Vasak M, Grutter MG. Structure of the mammalian NOS regulator dimethylarginine dimethylaminohydrolase: a basis for the design of specific inhibitors. Structure. 2006 May;14(5):901-911. PMID:16698551 doi:10.1016/j.str.2006.03.006
Janssen W, Pullamsetti SS, Cooke J, Weissmann N, Guenther A, Schermuly RT. The role of dimethylarginine dimethylaminohydrolase (DDAH) in pulmonary fibrosis. The Journal of Pathology. 2012 Dec 12;229(2):242-249. Epub 2013 Jan. PMID: 23097221 doi:10.1002/path.4127/full
Palm F, Onozato ML, Luo Z, Wilcox CS. Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems. American Journal of Physiology. 2007 Dec 1;293(6):3227-3245. PMID:17933965 doi:10.1152/ajpheart.00998.2007
Rasheed M, Richter C, Chisty LT, Kirkpatrick J, Blackledge M, Webb MR, Driscoll PC. Ligand-dependent dynamics of the active site lid in bacterial Dimethyarginine Dimethylaminohydrolase. Biochemistry. 2014 Feb 18;53:1092-1104. PMCID:PMC3945819 doi:10.1021/bi4015924
Stone EM, Costello AL, Tierney DL, Fast W. Substrate-assisted cysteine deprotonation in the mechanism of Dimethylargininase (DDAH) from Pseudomonas aeruginosa. Biochemistry. 2006 May 2;45(17):5618-5630. PMID:16634643 doi:10.1021/bi052595m
