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-PcxL and HpxL are flavin-dependent, oxime-forming N-oxidases in phosphonocystoximic acid biosynthesis in.

-PcxL and HpxL are flavin-dependent, oxime-forming N-oxidases in phosphonocystoximic acid biosynthesis in.
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Goettge MN, Cioni JP, Ju KS, Pallitsch K, Metcalf WW,


Goettge MN, Cioni JP, Ju KS, Pallitsch K, Metcalf WW, (click to view)

Goettge MN, Cioni JP, Ju KS, Pallitsch K, Metcalf WW,

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The Journal of biological chemistry 2018 03 14() pii 10.1074/jbc.RA118.001721

Abstract

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 bysp. NRRL S-481 andNRRL 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., but not insp. NRRL S-481). Subsequent installation of the oxime moiety into either 2AEPn or (S)-1H2AEPn is predicted to be catalyzed by PcxL or HpxL fromsp. NRRL S-481 and S.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 ()-1H2AEPn.2AEPn was turned over at a 10-fold higher rate under saturating conditions than (R)- 1H2AEPn, resulting in a similar, but slightly lower k/KWe 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-oxidases that are broadly dispersed among bacteria.

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