6GG2

The structure of FsqB from Aspergillus fumigatus, a flavoenzyme of the amine oxidase family

Summary for 6GG2

• Entry DOI: 10.2210/pdb6gg2/pdb
• Descriptor: Amino acid oxidase fmpA, FLAVIN-ADENINE DINUCLEOTIDE (3 entities in total)
• Functional Keywords: flavoenzyme, amine oxidase family, oxidoreductase
• Biological source: Aspergillus fumigatus Af293
• Total number of polymer chains: 1
• Total formula weight: 55777.49

Authors

Pavkov-Keller, T.,Lahham, M.,Macheroux, P.,Gruber, K. (deposition date: 2018-05-02, release date: 2018-09-19, Last modification date: 2024-01-17)

Primary citation

Lahham, M.,Pavkov-Keller, T.,Fuchs, M.,Niederhauser, J.,Chalhoub, G.,Daniel, B.,Kroutil, W.,Gruber, K.,Macheroux, P.
Oxidative cyclization ofN-methyl-dopa by a fungal flavoenzyme of the amine oxidase family.
J. Biol. Chem., 293:17021-17032, 2018

PubMed Abstract: Flavin-dependent enzymes catalyze many oxidations, including formation of ring structures in natural products. The gene cluster for biosynthesis of fumisoquins, secondary metabolites structurally related to isoquinolines, in the filamentous fungus harbors a gene that encodes a flavoprotein of the amine oxidase family, termed (fumisoquin biosynthesis gene B). This enzyme catalyzes an oxidative ring closure reaction that leads to the formation of isoquinoline products. This reaction is reminiscent of the oxidative cyclization reported for berberine bridge enzyme and tetrahydrocannabinol synthase. Despite these similarities, amine oxidases and berberine bridge enzyme-like enzymes possess distinct structural properties, prompting us to investigate the structure-function relationships of FsqB. Here, we report the recombinant production and purification of FsqB, elucidation of its crystal structure, and kinetic analysis employing five putative substrates. The crystal structure at 2.6 Å resolution revealed that FsqB is a member of the amine oxidase family with a covalently bound FAD cofactor. -methyl-dopa was the best substrate for FsqB and was completely converted to the cyclic isoquinoline product. The absence of the -hydroxyl group, as in l--methyl-tyrosine, resulted in a 25-fold lower rate of reduction and the formation of the demethylated product l-tyrosine, instead of a cyclic product. Surprisingly, FsqB did not accept the d-stereoisomer of -methyltyrosine, in contrast to -methyl-dopa, for which both stereoisomers were oxidized with similar rates. On the basis of the crystal structure and docking calculations, we postulate a substrate-dependent population of distinct binding modes that rationalizes stereospecific oxidation in the FsqB active site.

PubMed: 30194285
DOI: 10.1074/jbc.RA118.004227

Experimental method

X-RAY DIFFRACTION (2.598 Å)