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PubMed2001

Human NADPH-P450 oxidoreductase modulates the level of cytochrome P450 CYP2D6 holoprotein via haem oxygenase-dependent and -independent pathways.

NADPH-P450 oxidoreductase (CPR) is essential for the activity of cytochrome P450 (P450). Previous studies demonstrated that CPR regulates the levels of various P450 isoforms in vitro. We investigated the mechanistic basis for this regulation. By transfection of Chinese hamster ovary DUKXB11 cells we obtained the cell line DUKX/2D6, which expressed human CYP2D6, a P450 isoform. Subsequently, DUKX/2D6 cells were transfected with human CPR cDNA to generate the cell line DUKX/2D6/CPR-3. Expression of recombinant CPR decreased the level of spectrally detectable CYP2D6 holoprotein in DUKX/2D6/CPR-3 cells by 70%, whereas the level of immunodetectable apoprotein remained unchanged. Addition of the radical scavenger DMSO increased levels of CYP2D6 holoenzyme in DUKX/2D6/CPR-3 cells but not in DUKX/2D6 cells. A similar effect was noted when cells were grown in the presence of hemin. Importantly, combined treatment with DMSO and hemin increased levels of CYP2D6 holoenzyme in DUKX/2D6/CPR-3 but not in DUKX/2D6 cells even further than either treatment alone. None of these treatments affected the level of immunodetectable CYP2D6. This demonstrates that expression of CPR increases production of damaging radicals but also that CPR may alter haem homoeostasis. In agreement with this, the activity of haem oxygenase, a rate-limiting enzyme in haem metabolism, was compared with that in DUKX/DHFR control cells (expressing dihydrofolate reductase), and was 3-fold higher in DUKX/2D6/CPR-3 but similar in DUKX/2D6 cells. Furthermore, treatment of cells with sodium arsenite increased levels of haem oxygenase concomitant with a marked decrease of spectrally detectable CYP2D6 and a rise in levels of ferritin, which sequesters free iron released from the destruction of haem. These data demonstrate that CPR regulates P450 activity by supplying electrons and also by altering P450 levels via radical-and haem oxygenase-mediated pathways.

Animals↗
PubMed1968

Catechol oxygenase induction in Pseudomonas aeruginosa.

1. The transfer from benzenesulphonate to benzoate as a growth substrate for Pseudomonas aeruginosa strain A resulted in a change in the enzymic route by which catechol was degraded; at intermediate stages it was possible to obtain cells containing the enzymes of both the ;ortho' and ;meta' metabolic pathways. 2. A similar result was effected by the reverse transfer, benzoate to benzenesulphonate. 3. Catechol itself always elicited a catechol 2,3-oxygenase in uninduced cells, but the product of this reaction, 2-hydroxymuconic semialdehyde, and biochemically related compounds such as 4-hydroxy-2-oxovalerate, unexpectedly induced a catechol 1,2-oxygenase. 4. Both types of catechol oxygenase are strongly repressed by the metabolic end products of both the ;ortho' and ;meta' pathways, but there was no inhibition of enzymic activity by these end products.

Benzoates↗
PubMed1977

The soluble methane mono-oxygenase of Methylococcus capsulatus (Bath). Its ability to oxygenate n-alkanes, n-alkenes, ethers, and alicyclic, aromatic and heterocyclic compounds.

1. Methane mono-oxygenase of Methylococcus capsulatus (Bath) catalyses the oxidation of various substituted methane derivatives including methanol. 2. It is a very non-specific oxygenase and, in some of its catalytic properties, apparently resembles the analogous enzyme from Methylomonas methanica but differs from those found in Methylosinus trichosporium and Methylomonas albus. 3. CO is oxidized to CO2. 4. C1-C8 n-alkanes are hydroxylated, yielding mixtures of the corresponding 1- and 2-alcohols; no 3- or 4-alcohols are formed. 5. Terminal alkenes yield the corresponding 1,2-epoxides. cis- or trans-but-2-ene are each oxidized to a mixture of 2,3-epoxybutane and but-2-en-1-ol with retention of the cis or trans configuration in both products; 2-butanone is also formed from cis-but-2-ene only. 6. Dimethyl ether is oxidized. Diethyl ether undergoes sub-terminal oxidation, yielding ethanol and ethanal in equimolar amounts. 7. Methane mono-oxygenase also hydroxylates cyclic alkanes and aromatic compounds. However, styrene yields only styrene epoxide and pyridine yields only pyridine N-oxide. 8. Of those compounds tested, only NADPH can replace NADH as electron donor.

Alkanes↗
PubMed2006

Retinal is formed from apo-carotenoids in Nostoc sp. PCC7120: in vitro characterization of an apo-carotenoid oxygenase.

The sensory rhodopsin from Anabaena (Nostoc) sp. PCC7120 is the first cyanobacterial retinylidene protein identified. Here, we report on NosACO (Nostoc apo-carotenoid oxygenase), encoded by the ORF (open reading frame) all4284, as the candidate responsible for the formation of the required chromophore, retinal. In contrast with the enzymes from animals, NosACO converts beta-apo-carotenals instead of beta-carotene into retinal in vitro. The identity of the enzymatic products was proven by HPLC and gas chromatography-MS. NosACO exhibits a wide substrate specificity with respect to chain lengths and functional end-groups, converting beta-apo-carotenals, (3R)-3-hydroxy-beta-apo-carotenals and the corresponding alcohols into retinal and (3R)-3-hydroxyretinal respectively. However, kinetic analyses revealed very divergent Km and Vmax values. On the basis of the crystal structure of SynACO (Synechocystis sp. PCC6803 apo-carotenoid oxygenase), a related enzyme showing similar enzymatic activity, we designed a homology model of the native NosACO. The deduced structure explains the absence of beta-carotene-cleavage activity and indicates that NosACO is a monotopic membrane protein. Accordingly, NosACO could be readily reconstituted into liposomes. To localize SynACO in vivo, a Synechocystis knock-out strain was generated expressing SynACO as the sole carotenoid oxygenase. Western-blot analyses showed that the main portion of SynACO occurred in a membrane-bound form.

Binding Sites↗
PubMed1982

Effects of protein-degradation inhibitors on the inactivation of tyrosine aminotransferase, tryptophan oxygenase and benzopyrene hydroxylase in isolated rat hepatocytes.

The following three potent inhibitors of hepatocytic proteolysis were investigated to see if they would inhibit the intracellular inactivation of enzymes: chymostatin and leupeptin (proteinase inhibitors) and methylamine (a lysosomotropic weak base). Chymostatin inhibited the inactivation of two of the three enzymes tested: tyrosine aminotransferase (EC 2.6.1.5) and tryptophan oxygenase (tryptophan 2,3-dioxygenase, EC 1.13.11.11). Leupeptin had no effect on any of the enzymes, whereas methylamine had only a weak inhibitory effect on tyrosine aminotransferase inactivation. Apparently proteolytic cleavage (probably by a non-lysosomal proteinase, since only chymostatin is effective) is involved in the inactivation of tyrosine aminotransferase and tryptophan oxygenase. The third enzyme, benzopyrene hydroxylase (flavoprotein-linked mono-oxygenase, EC 1.14.14.1), is probably inactivated by a non-proteolytic mechanism.

Animals↗
PubMed1985

Spectroscopic evidence for a photosensitive oxygenated state of ammonia mono-oxygenase.

Photoinactivation of ammonia oxidation by Nitrosomonas europaea cells by near-u.v. light was confirmed and further shown to occur with the same rate constant as loss of bromoethane-oxidation activity. Hydroxylamine oxidation was much less photosensitive. Protection against inactivation was afforded by anaerobiosis, organic substrates of ammonia mono-oxygenase such as bromoethane, or metal-ion-chelating agents such as thiourea. The presence of 10 mM-NH4+ or 1 mM-hydroxylamine made little difference, whereas hydrazine had a potentiating effect. Illumination of cells also caused a bleaching in the absorption spectrum around 380 nm, along with changes in the cytochrome gamma-band region. Similar effects below 400 nm were obtained when organic substrates and inhibitors of the mono-oxygenase were added to cells in the dark. The copper proteins haemocyanin and tyrosinase have a photosensitive oxygenated state with a near-u.v. absorption band of similar half-width. They also have a sensitivity to chelating agents similar to that of ammonia mono-oxygenase. The experimental results are explained in terms of a three-stage catalytic cycle analogous to that for tyrosinase. In resting cells most of the enzyme is believed to be in an oxygenated (Oxy) form, which absorbs maximally at 378 nm and is photosensitive. In the presence of a substrate, one O atom is inserted into the substrate and the other is reduced to water, leaving the enzyme in an oxidized (Met) state. This is followed by a two-electron reduction of the proposed binuclear copper site to give a reduced (Deoxy) state, which can bind O2 to complete the cycle.

Ammonia↗
PubMed1987

Demonstration of non-neural tryptophan 5-mono-oxygenase in mouse intestinal mucosa.

Tryptophan 5-mono-oxygenase was demonstrated and its activity was measured in mucosal extracts of the mouse digestive tract by means of highly sensitive h.p.l.c. detection. The intestinal enzyme was activated by anaerobic incubation with dithiothreitol, as are the enzymes from mouse mastocytoma cells and bovine pineal gland. The dithiothreitol-enhanced activity was highest at the proximal portion of colon followed by that at the duodenum, where the unenhanced activity/enhanced activity ratio was highest. The enzymic and immunochemical properties of the intestinal tryptophan 5-mono-oxygenase were similar to those of the mastocytoma enzyme. In contrast, the intestinal enzyme was immunochemically different from brain tryptophan 5-mono-oxygenase. The possibility that connective tissue and/or mucosal mast cells are responsible for some of the enzyme activity of the duodenal mucosa was ruled out by the demonstration of the activity in extracts from a mast-cell-deficient mutant mouse (W/Wv). The enzyme in the duodenum was found to reside between the upper villus region and the bottom of the crypt, suggesting that it is mainly of enterochromaffin cell and not of submucosal nerve plexus origin.

Alkaline Phosphatase↗
PubMed1989

A stopped-flow kinetic study of soluble methane mono-oxygenase from Methylococcus capsulatus (Bath).

1. The roles of the three protein components of soluble methane mono-oxygenase were investigated by the use of rapid-reaction techniques. The transfer of electrons through the enzyme complex from NADH to methane/O2 was also investigated. 2. Electron transfer from protein C, the reductase component, to protein A, the hydroxylase component, was demonstrated. Protein C was shown to undergo a three-electron--one-electron catalytic cycle. The interaction of protein C with NADH was investigated. Reduction of protein C was shown to be rapid, and a charge-transfer interaction between reduced FAD and NAD+ was observed; this intermediate was also found in static titration experiments. Thus the binding of NADH, the reduction of protein C and the intramolecular transfer of electrons through protein C were shown to be much more rapid than the turnover rate of methane mono-oxygenase. 3. The rate of transfer of electrons from protein C to protein A was shown to be lower than the reduction of protein C but higher than the turnover rate of methane mono-oxygenase. Association of the proteins was not rate-limiting. The amount of protein A present in the system had a small effect on the rate of reduction of protein C, indicating some co-operativity between the two proteins. 4. Protein B was shown to prevent electron transfer between protein C and protein A in the absence of methane. On addition of saturating concentrations of methane electron transfer was restored. With saturating concentrations of methane and O2 the observed rate constant for the conversion of methane into methanol was 0.26 s-1 at 18 degrees C. 5. By the use of [2H4]methane it was demonstrated that C-H-bond breakage is likely to be the rate-limiting step in the conversion of methane into methanol.

Kinetics↗
PubMed1973

Messenger RNA for hepatic tryptophan oxygenase: its partial purification, its translation in a heterologous cell-free system, and its control by glucocorticoid hormones.

Messenger RNA from rat liver was partially purified by chromatography on cellulose on the basis of its poly(A) content. Microgram amounts of this RNA stimulate protein synthesis manyfold in a heterologous cell-free system, derived from Krebs ascites cells supplemented with reticulocyte initiation factors. The messenger RNA directs the initiation, synthesis, and release of a product that was identified as complete subunits of hepatic tryptophan oxygenase (EC 1.13.1.12) by immunoprecipitation with monovalent antibodies prepared against homogeneous tryptophan oxygenase and subsequent sodium dodecyl sulfate-polyacrylamide electrophoresis of the solubilized immunoprecipitate. This may represent the first complete translation in a heterologous system of a mammalian messenger RNA coding for an enzyme protein. Analysis of the messenger RNA content of the liver after glucocorticoid administration demonstrates that the hormonally enhanced rate of synthesis of tryptophan oxygenase is accompanied by an increased quantity of its corresponding messenger RNA.

Animals↗
PubMed1975

Control of the mRNA for hepatic tryptophan oxygenase during hormonal and substrate induction.

Glucocorticoid hormones increase the level of hepatic tryptophan oxygenase (EC 1.13.11.11; L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing) by increasing its rate of synthesis. Studies were performed to determine whether this induction is mediated by controlling the level of the mRNA for tryptophan oxygenase of by changing the translational efficiency of a fixed level of mRNA. Activity of tryptophan oxygenase mRNA was quantitated in a Krebs ascites cell-free, protein-synthesizing system, supplemented with tRNA and rabbit reticulocyte initiation factors. De novo synthesis of the protomeric unit(s) of the enzyme was a linear function of the amount of mRNA added. Time course and dose-response studies in which the enzyme level and mRNA activity in livers from rats injected with inducing doses of hydrocortisone were compared indicate that the induction of this enzyme is accompanied by a proportional increase in the level of its mRNA. This was true for mRNA isolated from total liver as well as from cytoplasmic polysomes. Induction of the enzyme by its substrate, tryptophan, however, was not accompanied by a parallel increase in mRNA activity.

Animals↗
PubMed1996

Heme iron reduction and catalysis by a nitric oxide synthase heterodimer containing one reductase and two oxygenase domains.

Inducible nitric oxide (NO) synthase (iNOS) is comprised of an oxygenase domain containing heme, tetrahydrobiopterin, the substrate binding site, and a reductase domain containing FAD, FMN, calmodulin, and the NADPH binding site. Enzyme activity requires a dimeric interaction between two oxygenase domains with the reductase domains attached as monomeric extensions. To understand how dimerization activates iNOS, we synthesized an iNOS heterodimer comprised of one full-length subunit and one histidine-tagged subunit that was missing its reductase domain. The heterodimer was purified using nickel-Sepharose and 2',5'-ADP affinity chromatography. The heterodimer catalyzed NADPH-dependent NO synthesis from L-arginine at a rate of 52 +/- 6 nmol of NO/min/nmol of heme, which is half the rate of purified iNOS homodimer. Heterodimer NO synthesis was associated with reduction of only half of its heme iron by NADPH, in contrast with near complete heme iron reduction in an iNOS homodimer. Full-length iNOS monomer preparations could not synthesize NO nor catalyze NADPH-dependent heme iron reduction. Thus, dimerization activates NO synthesis by enabling electrons to transfer between the reductase and oxygenase domains. Although a single reductase domain can reduce only one of two hemes in a dimer, this supports NO synthesis from L-arginine.

Animals↗
PubMed1997

Oxidation of alpha-meso-formylmesoheme by heme oxygenase. Electronic control of the reaction regiospecificity.

The oxidation of heme to biliverdin IXalpha by heme oxygenase involves regiospecific alpha-meso-hydroxylation followed by extrusion of the alpha-meso-carbon as CO. In an earlier study, enzymatic oxidation of the four meso-methylmesoheme isomers suggested that the reaction regiospecificity is sensitive to the electronic properties of the meso-methyl group (Torpey, J. W., and Ortiz de Montellano, P. R. (1996) J. Biol. Chem. 271, 26067-26073), although we could not exclude the possibility that the altered reaction regiochemistry was due to perturbation of the porphyrin structure by the meso-substituent. To examine this possibility, we have synthesized the four meso-formylmesoporphyrin isomers and have examined their oxidation by heme oxygenase. The meso-formyl and meso-methyl substituents differ in that the former is electron withdrawing and the latter is electron donating. In contrast to alpha-meso-methylmesoheme, which is exclusively oxidized at the methyl-substituted position, alpha-meso-formylmesoheme is exclusively oxidized at a non-formyl-substituted meso-carbon. The finding that the methyl and formyl groups channel the reaction regiospecificity in opposite directions establishes that the regiochemistry of the heme oxygenase reaction is primarily under electronic rather than steric control. It also confirms that the oxidation involves electrophilic addition of the oxygen to the porphyrin ring.

Biliverdine↗
PubMed1998

The oxygen and carbon monoxide reactions of heme oxygenase.

The O2 and CO reactions with the heme, alpha-hydroxyheme, and verdoheme complexes of heme oxygenase have been studied. The heme complexes of heme oxygenase isoforms-1 and -2 have similar O2 and CO binding properties. The O2 affinities are very high, KO2 = 30-80 microM-1, which is 30-90-fold greater than those of mammalian myoglobins. The O2 association rate constants are similar to those for myoglobins (kO2' = 7-20 microM-1 s-1), whereas the O2 dissociation rates are remarkably slow (kO2 = 0.25 s-1), implying the presence of very favorable interactions between bound O2 and protein residues in the heme pocket. The CO affinities estimated for both isoforms are only 1-6-fold higher than the corresponding O2 affinities. Thus, heme oxygenase discriminates much more strongly against CO binding than either myoglobin or hemoglobin. The CO binding reactions with the ferrous alpha-hydroxyheme complex are similar to those of the protoheme complex, and hydroxylation at the alpha-meso position does not appear to affect the reactivity of the iron atom. In contrast, the CO affinities of the verdoheme complexes are >10,000 times weaker than those of the heme complexes because of a 100-fold slower association rate constant (kCO' approximately 0. 004 microM-1 s-1) and a 300-fold greater dissociation rate constant (kCO approximately 3 s-1) compared with the corresponding rate constants of the protoheme and alpha-hydroxyheme complexes. The positive charge on the verdoporphyrin ring causes a large decrease in reactivity of the iron.

Animals↗
PubMed1998

Identification of histidine 45 as the axial heme iron ligand of heme oxygenase-2.

A truncated, soluble, and enzymatically active form of human heme oxygenase-2 (DeltaHHO2) was expressed in Escherichia coli. To identify the axial heme ligand of HO-2, His-45 to Ala (DeltaH45A) and His-152 to Ala (DeltaH152A) mutants have been prepared using this expression system. DeltaH45A could form a 1:1 complex with hemin but was completely devoid of the heme degradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-DeltaH45A complex. The DeltaH152A mutant was expressed as an inclusion body and was recovered from the lysis pellet by dissolution in urea followed by dialysis. The solubilized fraction obtained, however, was composed of a mixture of a functional enzyme and an inactive fraction. The inactive fraction was removed by Sephadex G-75 column chromatography since it eluted out of the column at the void volume. The gel filtration-purified DeltaH152A exhibited spectroscopic and enzymatic properties identical to those of wild-type. We conclude, in contrast to the previous reports (McCoubrey and Maines (1993) Arch. Biochem. Biophys. 302, 402-408; McCoubrey, W. K., Jr., Huang, T. J., and Maines, M. (1997) J. Biol. Chem. 272, 12568-12574), that His-45, but not His-152, in heme oxygenase isoform-2 is the proximal ligand of the heme and is essential for the heme degradation activity of the enzyme. His-152 appears to play a structural role in stabilization of the heme oxygenase protein.

Electron Spin Resonance Spectroscopy↗
PubMed1999

Ferric alpha-hydroxyheme bound to heme oxygenase can be converted to verdoheme by dioxygen in the absence of added reducing equivalents.

Whether or not reducing equivalents are indispensable for the conversion of ferric alpha-hydroxyheme bound to heme oxygenase-1 to verdoheme remains controversial (Matera, K. M., Takahashi, S., Fujii, H., Zhou, H., Ishikawa, K., Yoshimura, T., Rousseau, D. L., Yoshida, T., and Ikeda-Saito, M. (1996) J. Biol. Chem. 271, 6618-6624; Liu, Y., Moënne-Loccoz, P., Loehr, T. M., and Ortiz de Montellano, P. R. (1997) J. Biol. Chem. 272, 6906-6917). To resolve this controversy, we have prepared a ferric alpha-hydroxyheme-heme oxygenase-1 complex and titrated the complex with O2 under strictly anaerobic conditions. The formation of verdoheme was monitored by optical and electron spin resonance spectroscopies. Electron spin resonance spectra of the complex showed that alpha-hydroxyheme exists as a mixture of resonance structures composed of the iron(III) porphyrin and the iron(II) porphyrin pi neutral radical. Upon addition of CO the latter species becomes dominant. The results obtained from these titration experiments indicate that alpha-hydroxyheme can be converted to verdoheme by an approximately equimolar amount of O2 without any requirement for exogenous electrons. The verdoheme formed from alpha-hydroxyheme was shown to be in the ferrous oxidation state by the addition of CO or potassium ferricyanide to the resultant verdoheme-heme oxygenase-1 complex.

Electron Spin Resonance Spectroscopy↗
PubMed2004

Heme oxygenase-2 is activated by calcium-calmodulin.

The heme oxygenase family of enzymes catalyzes the metabolism of heme to biliverdin, ferrous iron, and carbon monoxide (CO). At least two isoforms exist, heme oxygenase-1 (HO1) and heme oxygenase-2 (HO2), which are encoded by separate genes. HO2 is selectively enriched in neurons, and substantial evidence suggests that HO2-derived CO functions as a neurotransmitter/neuromodulator. However, a molecular mechanism for the rapid activation of HO2 during neuronal activity has not been described. Through a yeast two-hybrid screen we identified calmodulin as a potential regulator of HO2 activity. Calmodulin binds with nanomolar affinity to HO2 in a calcium-dependent manner via a canonical 1-10 motif, resulting in a 3-fold increase in catalytic activity. Mutations within this motif block calmodulin binding and calcium-dependent stimulation of enzyme activity in vitro and in intact cells. The calcium mobilizing agents ionomycin and glutamate stimulate endogenous HO2 activity in primary cortical cultures, establishing in vivo relevance. Calcium-calmodulin provides a mechanism for rapid and transient activation of HO2 during neuronal activity.

Animals↗
PubMed2002

Interactions between the isolated oxygenase and reductase domains of neuronal nitric-oxide synthase: assessing the role of calmodulin.

Nitric-oxide synthase (NOS) is a fusion protein composed of an oxygenase domain with a heme-active site and a reductase domain with an NADPH binding site and requires Ca(2+)/calmodulin (CaM) for NO formation activity. We studied NO formation activity in reconstituted systems consisting of the isolated oxygenase and reductase domains of neuronal NOS with and without the CaM binding site. Reductase domains with 33-amino acid C-terminal truncations were also examined. These were shown to have faster cytochrome c reduction rates in the absence of CaM. N(G)-hydroxy-l-Arg, an intermediate in the physiological NO synthesis reaction, was found to be a viable substrate. Turnover rates for N(G)-hydroxy-l-Arg in the absence of Ca(2+)/CaM in most of the reconstituted systems were 2.3-3.1 min(-1). Surprisingly, the NO formation activities with CaM binding sites on either reductase or oxygenase domains were decreased dramatically on addition of Ca(2+)/CaM. However, NADPH oxidation and cytochrome c reduction rates were increased by the same procedure. Activation of the reductase domains by CaM addition or by C-terminal deletion failed to increase the rate of NO synthesis. Therefore, both mechanisms appear to be less important than the domain-domain interaction, which is controlled by CaM binding in wild-type neuronal NOS, but not in the reconstituted systems.

Animals↗
PubMed2003

CloR, a bifunctional non-heme iron oxygenase involved in clorobiocin biosynthesis.

The aminocoumarin antibiotics novobiocin and clorobiocin contain a 3-dimethylallyl-4-hydroxybenzoate (3DMA-4HB) moiety. The biosynthesis of this moiety has now been identified by biochemical and molecular biological studies. CloQ from the clorobiocin biosynthetic gene cluster in Streptomyces roseochromogenes DS 12976 has recently been identified as a 4-hydroxyphenylpyruvate-3-dimethylallyltransferase. In the present study, the enzyme CloR was overexpressed in Escherichia coli, purified, and identified as a bifunctional non-heme iron oxygenase, which converts 3-dimethylallyl-4-hydroxyphenylpyruvate (3DMA-4HPP) via 3-dimethylallyl-4-hydroxymandelic acid (3DMA-4HMA) to 3DMA-4HB by two consecutive oxidative decarboxylation steps. In 18O2 labeling experiments we showed that two oxygen atoms are incorporated into the intermediate 3DMA-4HMA in the first reaction step, but only one further oxygen is incorporated into the final product 3DMA-4HB during the second reaction step. CloR does not show sequence similarity to known oxygenases. It apparently presents a novel member of the diverse family of the non-heme iron (II) and alpha-ketoacid-dependent oxygenases, with 3DMA-4HPP functioning both as an alpha-keto acid and as a hydroxylation substrate. The reaction catalyzed by CloR represents a new pathway for the formation of benzoic acids in nature.

Aminocoumarins↗