Enzymes
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- Name help_outline AH2 Identifier CHEBI:17499 Charge 0 Formula RH2 SMILEShelp_outline *([H])[H] 2D coordinates Mol file for the small molecule Search links Involved in 2,799 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline α-N-dichloroacetyl-p-aminophenylserinol Identifier CHEBI:47325 (CAS: 7411-64-5) help_outline Charge 0 Formula C11H14Cl2N2O3 InChIKeyhelp_outline BFLNGKUCFYKCFZ-RKDXNWHRSA-N SMILEShelp_outline C1=C([C@H]([C@H](NC(C(Cl)Cl)=O)CO)O)C=CC(=C1)N 2D coordinates Mol file for the small molecule Search links Involved in 1 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline O2 Identifier CHEBI:15379 (CAS: 7782-44-7) help_outline Charge 0 Formula O2 InChIKeyhelp_outline MYMOFIZGZYHOMD-UHFFFAOYSA-N SMILEShelp_outline O=O 2D coordinates Mol file for the small molecule Search links Involved in 2,709 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline A Identifier CHEBI:13193 Charge Formula R SMILEShelp_outline * 2D coordinates Mol file for the small molecule Search links Involved in 2,870 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline chloramphenicol Identifier CHEBI:17698 (Beilstein: 2225532; CAS: 56-75-7) help_outline Charge 0 Formula C11H12Cl2N2O5 InChIKeyhelp_outline WIIZWVCIJKGZOK-RKDXNWHRSA-N SMILEShelp_outline C1=C([C@H]([C@H](NC(C(Cl)Cl)=O)CO)O)C=CC(=C1)[N+]([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 4 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H2O Identifier CHEBI:15377 (Beilstein: 3587155; CAS: 7732-18-5) help_outline Charge 0 Formula H2O InChIKeyhelp_outline XLYOFNOQVPJJNP-UHFFFAOYSA-N SMILEShelp_outline [H]O[H] 2D coordinates Mol file for the small molecule Search links Involved in 6,204 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:58884 | RHEA:58885 | RHEA:58886 | RHEA:58887 | |
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Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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CmlI N-oxygenase catalyzes the final three steps in chloramphenicol biosynthesis without dissociation of intermediates.
Komor A.J., Rivard B.S., Fan R., Guo Y., Que L. Jr., Lipscomb J.D.
CmlI catalyzes the six-electron oxidation of an aryl-amine precursor (NH<sub>2</sub>-CAM) to the aryl-nitro group of chloramphenicol (CAM). The active site of CmlI contains a (hydr)oxo- and carboxylate-bridged dinuclear iron cluster. During catalysis, a novel diferric-peroxo intermediate P is form ... >> More
CmlI catalyzes the six-electron oxidation of an aryl-amine precursor (NH<sub>2</sub>-CAM) to the aryl-nitro group of chloramphenicol (CAM). The active site of CmlI contains a (hydr)oxo- and carboxylate-bridged dinuclear iron cluster. During catalysis, a novel diferric-peroxo intermediate P is formed and is thought to directly effect oxygenase chemistry. Peroxo intermediates can facilitate at most two-electron oxidations, so the biosynthetic pathway of CmlI must involve at least three steps. Here, kinetic techniques are used to characterize the rate and/or dissociation constants for each step by taking advantage of the remarkable stability of P in the absence of substrates (decay t<sub>1/2</sub> = 3 h at 4 °C) and the visible chromophore of the diiron cluster. It is found that diferrous CmlI (CmlI<sup>red</sup>) can react with NH<sub>2</sub>-CAM and O<sub>2</sub> in either order to form a P-NH<sub>2</sub>-CAM intermediate. P-NH<sub>2</sub>-CAM undergoes rapid oxygen transfer to form a diferric CmlI (CmlI<sup>ox</sup>) complex with the aryl-hydroxylamine [NH(OH)-CAM] pathway intermediate. CmlI<sup>ox</sup>-NH(OH)-CAM undergoes a rapid internal redox reaction to form a CmlI<sup>red</sup>-nitroso-CAM (NO-CAM) complex. O<sub>2</sub> binding results in formation of P-NO-CAM that converts to CmlI<sup>ox</sup>-CAM by enzyme-mediated oxygen atom transfer. The kinetic analysis indicates that there is little dissociation of pathway intermediates as the reaction progresses. Reactions initiated by adding pathway intermediates from solution occur much more slowly than those in which the intermediate is generated in the active site as part of the catalytic process. Thus, CmlI is able to preserve efficiency and specificity while avoiding adventitious chemistry by performing the entire six-electron oxidation in one active site. << Less
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CmlI is an N-oxygenase in the biosynthesis of chloramphenicol.
Lu H., Chanco E., Zhao H.
The N-oxygenation of an amine group is one of the steps in the biosynthesis of the antibiotic chloramphenicol. The non-heme di-iron enzyme CmlI was identified as the enzyme catalyzing this reaction through bioinformatics studies and reconstitution of enzymatic activity. In vitro reconstitution was ... >> More
The N-oxygenation of an amine group is one of the steps in the biosynthesis of the antibiotic chloramphenicol. The non-heme di-iron enzyme CmlI was identified as the enzyme catalyzing this reaction through bioinformatics studies and reconstitution of enzymatic activity. In vitro reconstitution was achieved using phenazine methosulfate and NADH as electron mediators, while in vivo activity was demonstrated in <i>Escherichia coli</i> using two substrates. Kinetic analysis showed a biphasic behavior of the enzyme. Oxidized hydroxylamine and nitroso compounds in the reaction were detected both in vitro and in vivo based on LC-MS. The active site metal was confirmed to be iron based on a ferrozine assay. These findings provide new insights into the biosynthesis of chloramphenicol and could lead to further development of CmlI as a useful biocatalyst. << Less
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Diiron monooxygenases in natural product biosynthesis.
Komor A.J., Jasniewski A.J., Que L., Lipscomb J.D.
Covering: up to 2017 The participation of non-heme dinuclear iron cluster-containing monooxygenases in natural product biosynthetic pathways has been recognized only recently. At present, two families have been discovered. The archetypal member of the first family, CmlA, catalyzes β-hydroxylation ... >> More
Covering: up to 2017 The participation of non-heme dinuclear iron cluster-containing monooxygenases in natural product biosynthetic pathways has been recognized only recently. At present, two families have been discovered. The archetypal member of the first family, CmlA, catalyzes β-hydroxylation of l-p-aminophenylalanine (l-PAPA) covalently linked to the nonribosomal peptide synthetase (NRPS) CmlP, thereby effecting the first step in the biosynthesis of chloramphenicol by Streptomyces venezuelae. CmlA houses the diiron cluster in a metallo-β-lactamase protein fold instead of the 4-helix bundle fold of nearly every other diiron monooxygenase. CmlA couples O2 activation and substrate hydroxylation via a structural change caused by formation of the l-PAPA-loaded CmlP:CmlA complex. The other new diiron family is typified by two enzymes, AurF and CmlI, which catalyze conversion of aryl-amine substrates to aryl-nitro products with incorporation of oxygen from O2. AurF from Streptomyces thioluteus catalyzes the formation of p-nitrobenzoate from p-aminobenzoate as a precursor to the biostatic compound aureothin, whereas CmlI from S. venezuelae catalyzes the ultimate aryl-amine to aryl-nitro step in chloramphenicol biosynthesis. Both enzymes stabilize a novel type of peroxo-intermediate as the reactive species. The rare 6-electron N-oxygenation reactions of CmlI and AurF involve two progressively oxidized pathway intermediates. The enzymes optimize efficiency by utilizing one of the reaction pathway intermediates as an in situ reductant for the diiron cluster, while simultaneously generating the next pathway intermediate. For CmlI, this reduction allows mid-pathway regeneration of the peroxo intermediate required to complete the biosynthesis. CmlI ensures specificity by carrying out the multistep aryl-amine oxygenation without dissociating intermediate products. << Less
Nat Prod Rep 35:646-659(2018) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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An unusual peroxo intermediate of the arylamine oxygenase of the chloramphenicol biosynthetic pathway.
Makris T.M., Vu V.V., Meier K.K., Komor A.J., Rivard B.S., Muenck E., Que L. Jr., Lipscomb J.D.
Streptomyces venezuelae CmlI catalyzes the six-electron oxygenation of the arylamine precursor of chloramphenicol in a nonribosomal peptide synthetase (NRPS)-based pathway to yield the nitroaryl group of the antibiotic. Optical, EPR, and Mössbauer studies show that the enzyme contains a nonheme di ... >> More
Streptomyces venezuelae CmlI catalyzes the six-electron oxygenation of the arylamine precursor of chloramphenicol in a nonribosomal peptide synthetase (NRPS)-based pathway to yield the nitroaryl group of the antibiotic. Optical, EPR, and Mössbauer studies show that the enzyme contains a nonheme dinuclear iron cluster. Addition of O(2) to the diferrous state of the cluster results in an exceptionally long-lived intermediate (t(1/2) = 3 h at 4 °C) that is assigned as a peroxodiferric species (CmlI-peroxo) based upon the observation of an (18)O(2)-sensitive resonance Raman (rR) vibration. CmlI-peroxo is spectroscopically distinct from the well characterized and commonly observed cis-μ-1,2-peroxo (μ-η(1):η(1)) intermediates of nonheme diiron enzymes. Specifically, it exhibits a blue-shifted broad absorption band around 500 nm and a rR spectrum with a ν(O-O) that is at least 60 cm(-1) lower in energy. Mössbauer studies of the peroxo state reveal a diferric cluster having iron sites with small quadrupole splittings and distinct isomer shifts (0.54 and 0.62 mm/s). Taken together, the spectroscopic comparisons clearly indicate that CmlI-peroxo does not have a μ-η(1):η(1)-peroxo ligand; we propose that a μ-η(1):η(2)-peroxo ligand accounts for its distinct spectroscopic properties. CmlI-peroxo reacts with a range of arylamine substrates by an apparent second-order process, indicating that CmlI-peroxo is the reactive species of the catalytic cycle. Efficient production of chloramphenicol from the free arylamine precursor suggests that CmlI catalyzes the ultimate step in the biosynthetic pathway and that the precursor is not bound to the NRPS during this step. << Less