| Structural highlights
Function
LGOX_STRSQ Catalyzes the oxidative deamination of L-glutamate to 2-ketoglutarate along with the production of ammonia and hydrogen peroxide (PubMed:14769868, PubMed:22197816, Ref.2). Shows strict substrate specificity for L-glutamate, and exhibits only very weak activity with L-aspartate (Ref.2).[1] [2] [3]
Publication Abstract from PubMed
L-Amino acid oxidase (LAAO) is a flavoenzyme that catalyzes the oxidative deamination of L-amino acids, producing alpha-keto acids, ammonia, and hydrogen peroxide. Among LAAOs, L-glutamate oxidase (LGOX) from Streptomyces sp. X-119-6 exhibits exceptionally high substrate specificity for L-glutamate. LGOX is expressed as a homodimeric precursor and undergoes proteolytic processing for maturation. Structural studies revealed that LGOX comprises an FAD-binding domain, a substrate-binding domain, and a helical domain. Conserved residues W653, R124, and Y562 that recognize the alpha-amino and alpha-carboxyl groups of the substrate exist in the putative active site. R305 was identified as a key determinant for side-chain recognition; its substitution with Glu conferred specific activity toward L-arginine, effectively converting LGOX into an L-arginine oxidase. However, the putative substrate binding pocket includes an acidic residue, E617, undesirable for acidic substrates. Therefore, the mechanism of high specificity for L-glutamate remains unclear. To elucidate the molecular basis for the high substrate specificity of LGOX, we determined the structure of LGOX in complex with L-glutamate. Structural and mutational analyses revealed that E617 plays a critical role in substrate binding by aligning the side chain of R305. The loop at the entrance of the tunnel to the substrate-binding site regulates the access of the substrate to the site. Furthermore, E617F and E617K variants acquired L-tyrosine oxidase activity, providing insight into how specificity can be redirected. These findings clarify the substrate recognition mechanism of LGOX and underscore its potential as a robust scaffold for engineering novel amino acid oxidases with tailored specificities.
Substrate recognition mechanisms of L-glutamate oxidase from Streptomyces sp. and its conversion to L-tyrosine oxidase.,Ueda Y, Yano Y, Nakayama N, Takekawa N, Inagaki K, Imada K Protein Sci. 2026 Jan;35(1):e70432. doi: 10.1002/pro.70432. PMID:41432352[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Arima J, Tamura T, Kusakabe H, Ashiuchi M, Yagi T, Tanaka H, Inagaki K. Recombinant expression, biochemical characterization and stabilization through proteolysis of an L-glutamate oxidase from Streptomyces sp. X-119-6. J Biochem. 2003 Dec;134(6):805-12. PMID:14769868 doi:10.1093/jb/mvg206
- ↑ Utsumi T, Arima J, Sakaguchi C, Tamura T, Sasaki C, Kusakabe H, Sugio S, Inagaki K. Arg305 of Streptomyces L-glutamate oxidase plays a crucial role for substrate recognition. Biochem Biophys Res Commun. 2012 Jan 20;417(3):951-5. PMID:22197816 doi:10.1016/j.bbrc.2011.12.033
- ↑ Arima J, Sasaki C, Sakaguchi C, Mizuno H, Tamura T, Kashima A, Kusakabe H, Sugio S, Inagaki K. Structural characterization of L-glutamate oxidase from Streptomyces sp. X-119-6. FEBS J. 2009 Jul;276(14):3894-903. Epub 2009 Jun 15. PMID:19531050 doi:10.1111/j.1742-4658.2009.07103.x
- ↑ Ueda Y, Yano Y, Nakayama N, Takekawa N, Inagaki K, Imada K. Substrate recognition mechanisms of ʟ-glutamate oxidase from Streptomyces sp. and its conversion to ʟ-tyrosine oxidase. Protein Sci. 2026 Jan;35(1):e70432. PMID:41432352 doi:10.1002/pro.70432
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