engleski

Crystal structure of a fungal deglycating enzyme, fructosyl-amino acid oxidase (Amadoriase II)

Fructosyl-amino acid oxidases (FAOX) are bacterial and fungal enzymes that oxidize low molecular weight fructosamines at the C-N bond that link the fructose moiety to the amine. The Schiff base formed is unstable and hydrolyzes with the concomittant release of glucosone and the amine in its pristine stage. FAOX's can therefore be considered as deglycating enzymes ; however, these enzymes do not display activity toward glycated proteins. BLAST searches in fungi and evolutionary tree analysis indicated the presence of at least four different types of FAOX, that vary in their affinities for fructosamines depending on whether the sugar portion is linked to the amine bound to the carbon alpha or epsilon of the amino-acid. We report here the crystal structure of FAOX2 from A. fumigatus at 1.6 &Aring ; resolution in complex with an inhibitor, fructosyl-thioacetate. The structure of FAOX2 is very similar to sarcosine oxidase, its closest homologue. Comparison of the structure of FAOX2 with and without the inhibitor indicates conformational changes of the protein upon binding of the inhibitor. Residues potentially involved in substrate binding and specificity, FAD redox potential enhancement and conformational changes were identified and their roles are being investigated by mutagenesis. Measurements indicated that the active site is buried more than 15 &Aring ; under the surface of the enzyme, providing a possible explanation for the lack of activity of FAOX toward glycated proteins.

crystal structure; fructosyl-amino acid oxidase; Amadoriase II

nije evidentirano