| Critical catalytic functional groups in the mechanism of aspartate-beta-semialdehyde dehydrogenase. | |
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MedLine Citation:
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PMID: 15388927 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Aspartate-beta-semialdehyde dehydrogenase (ASADH) catalyzes the reductive dephosphorylation of beta-aspartyl phosphate to L-aspartate-beta-semialdehyde in the aspartate biosynthetic pathway. This pathway is not found in humans or other eukaryotic organisms, yet is required for the production of threonine, isoleucine, methionine and lysine in most microorganisms. The mechanism of this enzyme has been examined through the structures of two active-site mutants of ASADH from Haemophilus influenzae. Replacement of the enzyme active-site cysteine with serine (C136S) leads to a dramatic loss of catalytic activity caused by the expected decrease in nucleophilicity, but also by a change in the orientation of the serine hydroxyl group relative to the cysteine thiolate. In contrast, in the H277N active-site mutant the introduced amide is oriented in virtually the same position as that of the histidine imidazole ring. However, a shift in the position of the bound reaction intermediate to accommodate this shorter asparagine side chain, coupled with the inability of this introduced amide to serve as a proton acceptor, results in a 100-fold decrease in the catalytic efficiency of H277N relative to the native enzyme. These mutant enzymes have the same overall fold and high structural identity to native ASADH. However, small perturbations in the positioning of essential catalytic groups or reactive intermediates have dramatic effects on catalytic efficiency. |
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Authors:
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Julio Blanco; Roger A Moore; Christopher R Faehnle; Ronald E Viola |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. Date: 2004-09-23 |
Journal Detail:
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Title: Acta crystallographica. Section D, Biological crystallography Volume: 60 ISSN: 0907-4449 ISO Abbreviation: Acta Crystallogr. D Biol. Crystallogr. Publication Date: 2004 Oct |
Date Detail:
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Created Date: 2004-09-24 Completed Date: 2005-03-29 Revised Date: 2007-07-24 |
Medline Journal Info:
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Nlm Unique ID: 9305878 Medline TA: Acta Crystallogr D Biol Crystallogr Country: Denmark |
Other Details:
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Languages: eng Pagination: 1808-15 Citation Subset: IM |
Affiliation:
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Department of Chemistry, University of Toledo, Toledo, Ohio 43606, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Aspartate-Semialdehyde Dehydrogenase
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chemistry* Binding Sites Catalysis Catalytic Domain Cysteine / chemistry Haemophilus influenzae / enzymology Kinetics Models, Chemical Models, Molecular Mutation Protein Binding Protein Conformation Protein Structure, Secondary Protons Serine / chemistry |
| Chemical | |
Reg. No./Substance:
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0/Protons; 52-90-4/Cysteine; 56-45-1/Serine; EC 1.2.1.11/Aspartate-Semialdehyde Dehydrogenase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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