Article

Structural studies of the final enzyme in the alpha-aminoadipate pathway-saccharopine dehydrogenase from Saccharomyces cerevisiae.

Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3A 1A4.
Journal of Molecular Biology (impact factor: 4). 11/2007; 373(3):745-54. DOI:10.1016/j.jmb.2007.08.044 pp.745-54
Source: PubMed

ABSTRACT The 1.64 A structure of the apoenzyme form of saccharopine dehydrogenase (SDH) from Saccharomyces cerevisiae shows the enzyme to be composed of two domains with similar dinucleotide binding folds with a deep cleft at the interface. The structure reveals homology to alanine dehydrogenase, despite low primary sequence similarity. A model of the ternary complex of SDH, NAD, and saccharopine identifies residues Lys77 and Glu122 as potentially important for substrate binding and/or catalysis, consistent with a proton shuttle mechanism. Furthermore, the model suggests that a conformational change is required for catalysis and that residues Lys99 and Asp281 may be instrumental in mediating this change. Analysis of the crystal structure in the context of other homologous enzymes from pathogenic fungi and human sources sheds light into the suitability of SDH as a target for antimicrobial drug development.

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    Article: A structural basis for substrate selectivity and stereoselectivity in octopine dehydrogenase from Pecten maximus.
    Sander H J Smits, Andre Mueller, Lutz Schmitt, Manfred K Grieshaber
    [show abstract] [hide abstract]
    ABSTRACT: Octopine dehydrogenase [N(2)-(D-1-carboxyethyl)-L-arginine:NAD(+) oxidoreductase] (OcDH) from the adductor muscle of the great scallop Pecten maximus catalyzes the reductive condensation of l-arginine and pyruvate to octopine during escape swimming. This enzyme, which is a prototype of opine dehydrogenases (OpDHs), oxidizes glycolytically born NADH to NAD(+), thus sustaining anaerobic ATP provision during short periods of strenuous muscular activity. In contrast to some other OpDHs, OcDH uses only l-arginine as the amino acid substrate. Here, we report the crystal structures of OcDH in complex with NADH and the binary complexes NADH/l-arginine and NADH/pyruvate, providing detailed information about the principles of substrate recognition, ligand binding and the reaction mechanism. OcDH binds its substrates through a combination of electrostatic forces and size selection, which guarantees that OcDH catalysis proceeds with substrate selectivity and stereoselectivity, giving rise to a second chiral center and exploiting a "molecular ruler" mechanism.
    Journal of Molecular Biology 09/2008; 381(1):200-11. · 4.00 Impact Factor
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Keywords

antimicrobial drug development
 
apoenzyme form
 
conformational change
 
consistent
 
crystal structure
 
domains
 
homologous enzymes
 
human sources sheds light
 
low primary sequence similarity
 
mediating
 
pathogenic fungi
 
proton shuttle mechanism
 
residues Lys77
 
residues Lys99
 
SDH
 
similar dinucleotide binding folds
 
substrate binding
 
suitability
 

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