1. L-Aspartate oxidase from <em>Escherichia coli</em> I. Characterization of coenzyme binding and product inhibition.
- Author
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Mortarino, Michele, Negri, Armando, Tedeschi, Gabriella, Simonic, Tatjana, Duga, Stefano, Gassen, Hans Gunther, and Ronchi, Severino
- Subjects
FLAVOPROTEINS ,OXIDASES ,ESCHERICHIA coli ,PROTEINS ,MONOMERS ,ENZYMES ,MUTAGENESIS - Abstract
This paper reports the biochemical characterization of the flavoprotein L-aspartate oxidase from Escherichia coli. Modification of a previously published procedure allowed overexpression of the holoenzyme in an unproteolysed form. L-Aspartate oxidase is a monomer of 60 kDa containing 1 mol of non-covalently bound FAD/mol protein. A polarographic and two spectrophotometric coupled assays have been set up to monitor the enzymatic activity continuously. L-Aspartate oxidase was subjected to product inhibition since iminoaspartate, which results from the oxidation of L-aspartate, binds to the enzyme with a dissociation constant (K
d ) equal to 1.4 μM. The enzyme binds FAD by a simple second-order process with Kd 0.67 μM. Site-directed mutagenesis of the residues E43, G44, S45, F47 and Y48 located in the putative binding site of the isoallossazinic portion of FAD reduces the affinity for the coenzyme. [ABSTRACT FROM AUTHOR]- Published
- 1996
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