PcxL and HpxL are flavin-dependent, oxime-forming N-oxidases in phosphonocystoximic acid biosynthesis in Streptomyces
| Autor: | Joel P. Cioni, Michelle N. Goettge, William W. Metcalf, Kou San Ju, Katharina Pallitsch |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Oxidase test biology 010405 organic chemistry Stereochemistry Substrate (chemistry) Cell Biology Flavin group biology.organism_classification Oxime 01 natural sciences Biochemistry Streptomyces 0104 chemical sciences 03 medical and health sciences chemistry.chemical_compound 030104 developmental biology Biosynthesis chemistry Enzyme kinetics Streptomyces regensis Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 293:6859-6868 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.ra118.001721 |
| Popis: | Several oxime-containing small molecules have useful properties, including antimicrobial, insecticidal, anticancer, and immunosuppressive activities. Phosphonocystoximate and its hydroxylated congener, hydroxyphosphonocystoximate, are recently discovered oxime-containing natural products produced by Streptomyces sp. NRRL S-481 and Streptomyces regensis NRRL WC-3744, respectively. The biosynthetic pathways for these two compounds are proposed to diverge at an early step in which 2-aminoethylphosphonate (2AEPn) is converted to (S)-1-hydroxy-2-aminoethylphosphonate ((S)-1H2AEPn) in S. regensis but not in Streptomyces sp. NRRL S-481). Subsequent installation of the oxime moiety into either 2AEPn or (S)-1H2AEPn is predicted to be catalyzed by PcxL or HpxL from Streptomyces sp. NRRL S-481 and S. regensis NRRL WC-3744, respectively, whose sequence and predicted structural characteristics suggest they are unusual N-oxidases. Here, we show that recombinant PcxL and HpxL catalyze the FAD- and NADPH-dependent oxidation of 2AEPn and 1H2AEPn, producing a mixture of the respective aldoximes and nitrosylated phosphonic acid products. Measurements of catalytic efficiency indicated that PcxL has almost an equal preference for 2AEPn and (R)-1H2AEPn. 2AEPn was turned over at a 10-fold higher rate than (R)-1H2AEPn under saturating conditions, resulting in a similar but slightly lower kcat/Km. We observed that (S)-1H2AEPn is a relatively poor substrate for PcxL but is clearly the preferred substrate for HpxL, consistent with the proposed biosynthetic pathway in S. regensis. HpxL also used both 2AEPn and (R)-1H2AEPn, with the latter inhibiting HpxL at high concentrations. Bioinformatic analysis indicated that PcxL and HpxL are members of a new class of oxime-forming N-oxidases that are broadly dispersed among bacteria. |
| Databáze: | OpenAIRE |
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