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PubMed1983

Rapid reaction studies on the oxygenation reactions of catechol dioxygenase.

The reaction of oxygen with catechol 1,2-dioxygenase from Pseudomonas arvilla ATCC 23974 in complex with catechol, 4-methylcatechol, and 4-fluorocatechol has been studied using single turnover stopped flow spectrophotometry. Two sequential enzyme intermediates have been resolved and their visible spectra characterized by computer-assisted methods. These intermediates are spectrally similar to those observed in a similar study with protocatechuate dioxygenase (Bull, C., Ballou, D. P., and Otsuka, S. J. Biol. Chem. 256, 12681-12686 (1981), although the first intermediate seen with the latter enzyme was not observed in this study. The rate of formation of intermediate I is oxygen-dependent and also accelerated by electron-donating substituents on the C-4 of the substrate. This is consistent with the proposed substrate reduction of dioxygen to form a hydroperoxide. Intermediate I is thus suggested to be a 6-hydroperoxycyclohexa-3,5-diene-1-one. The decay of intermediate I is also accelerated by electron donors and is consistent with the rearrangement of intermediate hydroperoxide via an acyl migration mechanism. It is inconsistent with mechanisms involving nucleophilic attack at the carbonyl carbon. Intermediate II is proposed to be an enzyme-product complex based on the resemblance of its visible spectra to those of the benzoate complex of catechol 1,2-dioxygenase and enzyme-product complexes of protocatechuate dioxygenase. Careful 18O2-labeling experiments have shown that no label is lost to the solvent, implying that no free hydroxide forms during catalysis.

Catechol 1,2-Dioxygenase↗
PubMed1982

Effects of chronic treatment with thyroxine and estradiol on estrogen concentration in serum and on hepatic microsomal catechol estrogen formation in female rats.

The effects of chronic treatment with thyroxine (T4) and estradiol on hepatic microsomal metabolism of estrogens to catechol products were studied and the extent to which activity in vitro correlated with serum estradiol concentrations in vivo was assessed. Female rats were treated with either estradiol benzoate (EB; 56 micrograms/kg/day from silastic implants), T4 (50 micrograms/kg/day, s.c.) or combined EB + T4 for 35 days. Animals treated with EB + T4, but not T4 alone, showed a significant increase above controls both in the concentration of triiodothyronine in serum and food consumption. Serum concentrations of endogenous estradiol in untreated control and T4-treated animals were similar. Although both EB-treated groups received comparable doses of steroid from silastic implants, the concentration of estradiol in serum was 30% lower in EB + T4-treated animals than in animals treated with EB alone. Formation of catechol estrogen metabolites by hepatic microsomes was not significantly altered by EB and T4 administered separately, but enzyme activity was increased significantly with combined hormonal therapy. In contrast, microsomal hydroxylation of testosterone was not increased by treatment with EB + T4, data which suggest that total steroid hydroxylase activity was not enhanced by combined hormonal administration. Correlation analysis of microsomal catechol estrogen formation in vitro with serum concentrations of estradiol in vivo indicated related to the concentration of estrogen in serum only after coadministration of a low dose of T4 with EB.

Animals↗
PubMed1993

Purification and properties of a catechol oxidase from blood cells of the ascidian Pyura stolonifera.

A catechol oxidase (EC 1.10.3.1) was purified to homogeneity from blood cells of the ascidian Pyura stolonifera using gel filtration on Sephadex G-50 and hydrophobic interaction chromatography on PhenylSuperose. Two peaks of activity were eluted from PhenylSuperose, one with a decreasing salt gradient and the other with nonionic detergent. The latter represents an aggregated form of the enzyme. The enzyme has a molecular weight of 56 kd and shows a preference for catechols with uncharged hydrophobic side chains (e.g., 4-t-butylcatechol) but does not hydroxylate free tyrosine. Inhibition of the enzyme by diethyldithiocarbamic acid and thiol reagents implicate copper at the active site. Sequence analysis of a peptide generated by incubation with Staphylococcus aureus V8 protease demonstrated considerable homology to one of the conserved copper binding regions of tyrosinases. This enzyme is found in the same cells as the dopa-containing protein ferreascidin. When ferreascidin is incubated with the enzyme, its spectrum changes rapidly, indicating that the catechol oxidase uses it as a substrate. The P. stolonifera enzyme differs from an enzyme involved in adhesion, isolated from the mussels, M. edulis and G. demissa: it is isolated as a soluble enzyme that does not appear to exist as a latent precursor.

Amino Acid Sequence↗
PubMed1997

Peptide mapping and amino acid sequencing of two catechol 1,2-dioxygenases (CD I1 and CD I2) from Acinetobacter lwoffii K24.

The partial amino acid sequences of two catechol 1,2-dioxygenases (CD I1 and CD I2) from Acinetobacter lwoffii K24 have been determined by analysis of peptides after cleavages with endopeptidase Lys-C, endopeptidase Glu-C, trypsin, and chemicals (cyanogen bromide and BNPS-skatole). They include 248 amino acid sequences (4 fragments) of CD I1 and 211 amino acid sequences (5 fragments) of CD I2. Two enzymes have more than 50% sequence homology with type I catechol 1,2-dioxygenases and less than 30% sequence homology with type II catechol 1,2-dioxygenases. Two enzymes have similar hydropathy profiles in the N-terminal region, suggesting that they have similar secondary structures.

Acinetobacter↗
PubMed1997

An association between the allele coding for a low activity variant of catechol-O-methyltransferase and the risk for breast cancer.

Mounting evidence suggests that catechol metabolites of estradiol may contribute to the development of estrogen-induced cancers. O-Methylation, catalyzed by catechol-O-methyltransferase (COMT), inactivates catechol estrogens. COMT is polymorphic in the human population, with 25% of Caucasians being homozygous for a low activity allele of the enzyme (COMT(LL)). We hypothesized that low activity COMT may be a risk factor for human breast cancer and designed a PCR-based RFLP assay to determine COMT genotype in a cohort of 112 matched, nested case-control samples. In the total study population, the odds ratios for the association of breast cancer risk with COMT(HL) and COMT(LL) genotypes were 1.30 [confidence interval (CI), 0.66-2.58] and 1.45 (CI, 0.69-3.07), respectively. Postmenopausal COMT(LL) women had a greater than 2-fold increased risk of developing breast cancer [odds ratio (OR), 2.18; CI, 0.93-5.11]. The association of COMT(LL) with the development of postmenopausal breast cancer was stronger and statistically significant in those women with a body mass index >24.47 kg/m2 (OR, 3.58; CI, 1.07-11.98). When COMT(LL) was combined with either glutathione S-transferase (GST) M1 null or with GSTP1 Ile-105-Val/Val-105-Val (intermediate/low activity, respectively) genotypes, the risk for developing postmenopausal breast cancer was also significantly increased. Our findings suggest that the allele encoding low activity COMT may be an important contributor to the postmenopausal development of breast cancer in certain women.

Aged↗
PubMed1990

Inhibition of catechol-O-methyltransferase by N-(3,4-dihydroxyphenyl) maleimide.

Catechol-O-methyltransferase (COMT) is inhibited rapidly and irreversibly by N-(3,4-dihydroxyphenyl) maleimide. S-adenosylmethionine (AdoMet) and magnesium ions protect the enzyme from inactivation by this compound, but no protection is observed by the catechol substrate. However, the corresponding succinimide analogue shows a reversible inhibition of COMT, which is competitive with pyrocatecholphthalein and non-competitive with AdoMet. Amino-group reagents also inhibit COMT and this inhibition is protected by AdoMet, suggesting that sulphydryl and amino groups essential for activity are located in an AdoMet-binding site on COMT. The maleimide derivative may be considered to be an active-site directed inhibitor.

Animals↗
PubMedDate not supplied

[The neuroendocrine effects of neonatal exposure to an inhibitor of catechol-o-methyltransferase and of sex steroids].

The role of catechol-o-methyltransferase (COMT) in functional interrelationship between testosterone (T), catechol estrogens (CE) and catecholamines (CA) during cerebral sex differentiation (CSD) was investigated in experiments on Wistar rats. Sex dimorphism in the level of CA in the rat hypothalamus was revealed on the 10th day of life. Noradrenaline concentration in male rats was significantly higher than in the female rats (p less than 0.05). It was shown that isolated CA accumulation in the hypothalamus of 10-day female rats by means of direct suppression of COMT with tropolon (300 micrograms on the 5th and 7th days of life) was insufficient for masculinization of sex cycling regulation centers. At the same time tropolon administered in a dose of 100 micrograms on the 4th-10th days of life enhanced the sterilizing effect of T administered in a dose of 25 micrograms on the 4th day of life. The development of anovulatory sterility (AS) was observed in 100% of cases. The neonatal effect of 2-hydroxyestradiol-17 beta (2-OH-E2 50 micrograms on the 5th day of life) and tropolon (300 micrograms on the 5th and 7th days of life) was ineffective with relation to AS induction indicating the absence of the inductor role of 2-OH-E2 in CSD. A conclusion is that CSD is a result of combined action of androgens, their metabolites (4-hydroxylated CE isomers) and COMT-mediated CA.

Animals↗
PubMed1997

Graphical analysis of 6-fluoro-L-dopa trapping: effect of inhibition of catechol-O-methyltransferase.

UNLABELLED: Graphical methods to analyze tracer time-course data allow reliable quantitation of the rate of incorporation of tracer from plasma into a "trapped" kinetic component, even when the details of the kinetic model are unknown. Applications of the method over long time periods often expose the slow reversibility of the trapping process. In the extended graphical method, both trapping rate and a presumed first-order loss rate constant are estimated simultaneously from the time-course data. METHODS: We applied the extended graphical method to 6-fluoro-L-dopa (6-FD), simultaneously estimating the rate of uptake (Ki) and the rate constant for loss from the trapped component (K(loss)) in a single fitting procedure. We applied this approach to study the effects of two catechol-O-methyl-transferase inhibitors on the kinetics of 6-FD in cynomolgus monkeys. RESULTS: Inhibition of peripheral O-methylation with either inhibitor, confirmed by high-performance liquid chromatography analysis of labeled compounds in arterial plasma, had no significant effect on Ki, in agreement with previously reported studies. In contrast, tolcapone, a catechol-O-methyl-transferase inhibitor, having central effects in addition to peripheral effects at the dosage used, decreased K(loss) by 40% from control values (p < 0.002), whereas nitecapone, which has no known central activity, had no significant effect. CONCLUSION: This method provides insight into the neurochemical basis for the kinetic behavior of 6-FD in both health and disease and may be used to define the action of centrally active drugs that influence the metabolism of dopamine.

Animals↗
PubMed1989

Patterns of plasma levels of catechols in neurogenic orthostatic hypotension.

Patients with neurogenic orthostatic hypotension can have deficits in sympathetic neural function at any of several levels of the sympathetic neuraxis. We determined whether patterns of plasma levels of dopa, norepinephrine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid would distinguish patients with orthostatic hypotension associated with multiple system atrophy, pure autonomic failure, or deficiency of dopamine-beta-hydroxylase. Plasma levels of catechols were normal in most patients with multiple system atrophy, consistent with relatively intact peripheral sympathetic neurons; in contrast, most patients with pure autonomic failure had decreased levels of all four catechols, consistent with degenerative loss of sympathetic nerve endings. Patients with deficiency of dopamine-beta-hydroxylase had increased levels of dopa and dihydroxyphenylacetic acid and markedly decreased levels of norepinephrine and dihydroxyphenylglycol, suggesting compensatory increases in sympathetic nerve activity in the absence of norepinephrine biosynthesis. Subgroups of patients with pure autonomic failure or multiple system atrophy had low levels of norepinephrine with normal levels of dopa, dihydroxyphenylglycol, and dihydroxyphenylacetic acid, consistent with normal catecholamine biosynthesis and decreased postganglionic sympathetic nerve traffic or decreased exocytotic release from sympathetic nerve endings. The results demonstrate the value of examining patterns of plasma levels of catechols to elucidate mechanisms of neurogenic orthostatic hypotension.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2007

Reaction pathways involved in the mechanism of AlIII chelation with caffeic acid: catechol and carboxylic functions competition.

Density functional theory calculations on the AlIII-caffeic acid system are carried out to investigate the fixing mechanism of this metal ion to the two competing complexing sites in the ligand. This theoretical study was performed to explain the complex formation of 1:1 stoichiometry observed in aqueous medium at low pH values. Both complexation with the catechol and carboxylic functions are envisaged. The reaction pathways for the formation of these two chelates are calculated at the B3LYP/6-31G** level of theory. The complexation on the more acidic group is relatively straightforward and shows the intermediate formation of a monodentate complex followed by a chelation process. The complexation reaction pathway with the catechol function is more sophisticated, and several pathways are explored. Once more, the formation of a monodentate complex is achieved and the most favorable pathway for chelation involves the successive steps: 1) coordination of AlIII on the oxygen atom of a hydroxyl group, 2) deprotonation of this hydroxyl group, 3) ring closure with the other oxygen atom, and 4) deprotonation of the second hydroxyl. From an energetic point of view, this second pathway is more favorable. Notably the energy barrier necessary to form the chelate is lower for the catechol function than that calculated for the carboxylic group. The results of this purely theoretical study are in complete agreement with spectroscopic investigations performed on this system.

Journal Article↗
PubMed1998

Iron-binding catechols oxidating lignin and chlorolignin.

Iron-chelating low-molecular-weight compounds or catecholate siderophores have been suggested to be involved in wood biodegradation. To help in understanding the mechanism involved in the enzyme-like activity of catecholate siderophores, the oxidative properties of 2,3-dihydroxybenzoic acid (DHBA) and 3, 4-dihydroxyphenylacetic acid (DHPAA) chelated with iron were studied. The pH and catechol/Fe(III) ratios were optimized for o-dianisidine oxidation, obtaining a maximum at pH 7.0, in the absence of buffer, and a catechol/Fe(III) ratio of 1:2 to DHBA and 1:1 to DHPAA was found. Under these conditions, the catechols were able to reduce Fe(III) to Fe(II) acting like siderophore models. The Fe(III) complex of DHBA and of DHPAA degraded dioxane-lignin in 60% after 2 h and 85% after 24 h, respectively. DHBA/Fe(III) oxidized the bleaching effluent (E1) in 80% in 5 min under the studied conditions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Immobilization of functionally unstable catechol-2,3-dioxygenase greatly improves operational stability.

Thermophilic catechol 2,3-dioxygenase (EC 1.13.11.2) from Bacillus stearothermophilus has been immobilized on highly activated glyoxyl agarose beads. The enzyme could be fully immobilized at 4 degrees C and pH 10.05 with a high retention of activity (around 80%). Enzyme immobilized under these conditions showed little increase in thermostability compared with the soluble enzyme, but further incubation of immobilized enzyme at 25 degrees C and pH 10.05 for 3 h before borohydride reduction resulted in conjugates exhibiting a 100-fold increase in stability (c.f. the free enzyme). The stability of catechol 2,3-dioxygenase immobilized under these conditions was essentially independent of protein concentration whereas free enzyme was rapidly inactivated at low protein concentrations. An apparent stabilization factor of over 700-fold was recorded in the comparison of free and immobilized catechol 2,3-dioxygenases at protein concentrations of 10 µg/ml. Immobilization increased the 'optimum temperature' for activity by 20 degrees C, retained activity at substrate concentrations where the soluble enzyme was fully inactivated and enhanced the resistance to inactivation during catalysis. These results suggest that the immobilization of the enzyme under controlled conditions with the generation of multiple covalent links between the enzyme and matrix both stabilized the quaternary structure of the protein and increased the rigidity of the subunit structures.

Journal Article↗
PubMed1999

Design of PCR primers and gene probes for the general detection of bacterial populations capable of degrading aromatic compounds via catechol cleavage pathways.

For the general detection of bacterial populations capable of degrading aromatic compounds, two PCR primer sets were designed which can, respectively, amplify specific fragments from a wide variety of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) genes. The C12O-targeting primer set (C12O primers) was designed based on the homologous regions of 11 C12O genes listed in the GenBank, while the C23O-targeting one (C23O primers) was designed based on those of 17 known C23O genes. Oligonucleotide probes (C12Op and C23Op) were also designed from the internal homologous regions to identify the amplified fragments. The specificity of the primer sets and probes was confirmed using authentic bacterial strains known to carry the C12O and/or C23O genes used for the primer and probe design. Various authentic bacterial strains carrying neither C12O nor C23O genes were used as negative controls. PCR with the C12O primers amplified DNA fragments of the expected sizes from 5 of the 6 known C12O-carrying bacterial strains tested, and positive signals were obtained from 4 of the 5 amplified fragments on Southern hybridization with the C12Op. The C23O primers amplified DNA fragments of the expected size from all the 11 tested C23O-carrying bacterial strains used for their design, while the C23Op detected positive signals in the amplified fragments from 9 strains. On the other hand, no DNA fragments were amplified from the negative controls. To evaluate the applicability of the designed primers and probes for the general detection of aromatic compound-degrading bacteria, they were applied to wild-type phenol- and/or benzoate-degrading bacteria newly isolated from a variety of environments. The C12O and/or C23O primers amplified DNA fragments of the expected sizes from 69 of the 106 wild-type strains tested, while the C12Op and/or C23Op detected positive signals in the amplified fragments from 63 strains. These results suggest that our primer and probe systems can detect a considerable proportion of bacteria which can degrade aromatic compounds via catechol cleavage pathways.

Journal Article↗
PubMed1998

Tyrosinase Models. Synthesis, Structure, Catechol Oxidase Activity, and Phenol Monooxygenase Activity of a Dinuclear Copper Complex Derived from a Triamino Pentabenzimidazole Ligand.

The dicopper(II) complex with the ligand N,N,N',N',N"-pentakis[(1-methyl-2-benzimidazolyl)methyl]dipropylenetriamine (LB5) has been synthesized and structurally characterized. The small size and the quality of the single crystal required that data be collected using synchrotron radiation at 276 K. [Cu(2)(LB5)(H(2)O)(2)][ClO(4)](4): platelet shaped, P&onemacr;, a = 11.028 Å, b = 17.915 Å, c = 20.745 Å, alpha = 107.44 degrees, beta = 101.56 degrees, gamma = 104.89 degrees, V = 3603.7 Å(3), Z = 2; number of unique data, I >/= 2sigma(I) = 3447; number of refined parameters = 428; R = 0.12. The ligand binds the two coppers nonsymmetrically; Cu1 is coordinated through five N donors and Cu2 through the remaining three N donors, while two water molecules complete the coordination sphere. Cu1 has distorted TBP geometry, while Cu2 has distorted SP geometry. Voltammetric experiments show quasireversible reductions at the two copper centers, with redox potential higher for the CuN(3) center (0.40 V) and lower for the CuN(5) center (0.17 V). The complex binds azide in the terminal mode at the CuN(3) center with affinity lower than that exhibited by related dinuclear polyaminobenzimidazole complexes where this ligand is bound in the bridging mode. The catechol oxidase activity of [Cu(2)(LB5)](4+) has been examined in comparison with that exhibited by [Cu(2)(L-55)](4+) (L-55 = alpha,alpha'-bis{bis[(1-methyl-2-benzimidazolyl)methyl]amino}-m-xylene) and [Cu(2)(L-66)](4+) (L-66 = alpha,alpha'-bis{bis[2-(1-methyl-2-benzimidazolyl)ethyl]amino}-m-xylene) by studying the catalytic oxidation of 3,5-di-tert-butylcatechol in methanol/aqueous buffer pH 5.1. Kinetic experiments show that [Cu(2)(L-55)](4+) is the most efficient catalyst (rate constant 140 M(-1) s(-1)), followed by [Cu(2)(LB5)](4+) (60 M(-1) s(-1)), in this oxidation, while [Cu(2)(L-66)](4+) undergoes an extremely fast stoichiometric phase followed by a slow and substrate-concentration-independent catalytic phase. The catalytic activity of [Cu(2)(L-66)](4+), however, is strongly promoted by hydrogen peroxide, because this oxidant allows a fast reoxidation of the dicopper(I) complex during turnover. The activity of [Cu(2)(LB5)](4+) is also promoted by hydrogen peroxide, while that of [Cu(2)(L-55)](4+) is little affected. The phenol monooxygenase activity of [Cu(2)(LB5)](2+) has been compared with that of [Cu(2)(L-55)](2+) and [Cu(2)(L-66)](2+) by studying the ortho hydroxylation of methyl 4-hydroxybenzoate to give methyl 3,4-dihydroxybenzoate. The LB5 complex is much more selective than the other complexes since its reaction produces only catechol, while the main product obtained with the other complexes is an addition product containing a phenol residue condensed at ring position 2 of the catechol.

Journal Article↗
PubMed2004

Preparation and palladium-catalyzed cross-coupling of aryl triethylammonium bis(catechol) silicates with aryl triflates.

Pentavalent aryl and heteroaryl bis(catechol) silicates undergo palladium-catalyzed cross-coupling with aryl and heteroaryl triflates in the presence of a fluoride source in excellent yields. These solid, air-stable bis(catechol) silicates are prepared from a high-yielding displacement reaction between catechol and an aryl siloxane in the presence of an amine base. The cross-coupling reaction is tolerant of a wide range of electron-donating and electron-withdrawing groups. Several examples of di-ortho-substituted triflates are successfully coupled with these reagents.

Catalysis↗
PubMed2006

Interfacial electron transfer between the photoexcited porphyrin molecule and TiO2 nanoparticles: effect of catecholate binding.

Interfacial electron transfer (ET) dynamics of 5,10,15-trisphenyl-20-(3,4-dihydroxybenzene) porphyrin (TPP-cat) adsorbed on TiO2 nanoparticles has been studied by femtosecond transient absorption spectroscopy in the visible and near-IR region exciting at 400 and 800 nm. TPP-cat molecule forms a charge transfer (CT) complex with TiO2 nanoparticles through the catechol moiety with the formation of a five-membered ring. Optical absorption measurements have shown that the Q-band of TPP-cat interacts strongly with TiO2 due to chelation; however, the Soret band is affected very little. Optical absorption measurements indicate that the catechol moiety also interacts with TiO2 nanoparticles showing the characteristic band of pure catechol-TiO2 charge transfer (CT) in the visible region. Electron injection has been confirmed by monitoring the cation radical, instant bleach, and injected electron in the conduction band of TiO2 nanoparticles. Electron injection time has been measured to be < 100 fs and recombination kinetics has been best fitted with a multiexponential function, where the majority of the injected electrons come back to the parent cation radical with a time constant of approximately 800 fs for both excitation wavelengths. However, the reaction channel for the electron injection process has been found to be different for both wavelengths. Excitation at 800 nm, found to populate the CT state of the Q-band, and from the photoexcited CT state electron injection into the conduction band, takes place through diffusion. On the other hand, with excitation at 400 nm, a complicated reaction channel takes place. Excitation with 400 nm light excites both the CT band of Cat-TiO2 and also the Soret band of TPP-cat. We have discussed the reaction path in the TPP-cat/TiO2 system after exciting with both 400 and 800 nm laser light. We have also compared ET dynamics by exciting at both wavelengths.

Journal Article↗
PubMed2006

Probing the surface adsorption and photocatalytic degradation of catechols on TiO2 by solid-state NMR spectroscopy.

The local structure of the TiO2 surface modified with electron-donating bidentate ligands, such as catechols, has been investigated by solid-state NMR spectroscopy. The adsorption and degradation processes of catechols at the TiO2 surface were observed. The photocatalytic degradation mechanism of catechols at the TiO2 surface was interpreted in terms of the interfacial charge recombination reaction with conduction band electrons.

Adsorption↗
PubMed2003

The colicin G, H and X determinants encode microcins M and H47, which might utilize the catecholate siderophore receptors FepA, Cir, Fiu and IroN.

The colicin G producer Escherichia coli CA46, the colicin H producer E. coli CA58 and E. coli Nissle 1917 (DSM 6601) were shown to produce microcin H47 and the newly described microcin M. Both microcins were exported like colicin V by an RND-type export system, including TolC. The gene cluster encoding microcins H47 and M in strains CA46 and CA58 is nearly identical to that in strain DSM 6601, except that two additional genes are included. A Fur box identified in front of the microcin-encoding genes explained the observed iron regulation of microcin production. The catecholate siderophore receptors Fiu, Cir and FepA from E. coli and IroN, Cir and FepA from Salmonella were identified as receptors for microcins M, H47 and E492. IroN takes up the glucose-containing catecholate siderophore salmochelin, whose synthesis is encoded in the iro gene cluster found in Salmonella and certain, often uropathogenic, E. coli strains. A gene in this iro cluster, iroB, which encodes a putative glycosyltransferase, was also found in the microcin H47/M and microcin E492 gene clusters. These microcins could aid the producing strain in competing against enterobacteria that utilize catecholate siderophores.

Antimicrobial Cationic Peptides↗