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PubMed1987

Adduct formation between the cupric site of phenylalanine hydroxylase from Chromobacterium violaceum and 6,7-dimethyltetrahydropterin.

The interaction of pterin-dependent phenylalanine hydroxylase from Chromobacterium violaceum with the cofactor analogue 5-deaza-6-methyltetrahydropterin and the cofactor 6,7-dimethyltetrahydropterin (DMPH4) has been investigated by multifrequency electron spin resonance (ESR) spectroscopy. 5-Deaza-6-methyltetrahydropterin, which lacks the N-5 nitrogen present in the pyrazine ring of DMPH4, binds tightly to the cupric form of the enzyme; however, no changes are observed in the ESR parameters of the copper center. In contrast, the binding of DMPH4 (or 6-methyltetrahydropterin) shifts the ESR parameters (g and A) associated with the cupric enzyme. In addition, superhyperfine transitions were resolved and assigned to hyperfine splitting from nitrogen ligands. ESR spectra of the enzyme recorded in the presence of [5-14N]DMPH4 or [5-15N]DMPH4 were computer simulated and found to be consistent with pterin serving as a direct donor ligand to the copper center through the N-5 position.

Binding Sites↗
PubMed1989

Mechanistic studies on phenylalanine hydroxylase from Chromobacterium violaceum. Evidence for the formation of an enzyme-oxygen complex.

Steady-state kinetic analysis of pterin-dependent phenylalanine hydroxylase from Chromobacterium violaceum indicated that the enzyme follows a partially ordered reaction mechanism. The data suggested that oxygen is the first substrate to bind to the enzyme. This result was further supported by rapid-quench experiments in which the enzyme-oxygen complex was trapped to yield product. Additional support for the presence of an enzyme-oxygen complex was derived from magnetic susceptibility measurements of molecular oxygen in the presence and absence of cuprous phenylalanine hydroxylase. The magnetic susceptibility of dissolved oxygen decreased in the presence of the enzyme, supporting a direct oxygen-metal interaction.

Chromobacterium↗
PubMed2006

Unusual entropy-driven affinity of Chromobacterium violaceum lectin CV-IIL toward fucose and mannose.

The purple pigmented bacterium Chromobacterium violaceum is a dominant component of tropical soil microbiota that can cause rare but fatal septicaemia in humans. Its sequenced genome provides insight into the abundant potential of this organism for biotechnological and pharmaceutical applications and allowed an ORF encoding a protein that is 60% identical to the fucose binding lectin (PA-IIL) from Pseudomonas aeruginosa and the mannose binding lectin (RS-IIL) from Ralstonia solanacearum to be identified. The lectin, CV-IIL, has recently been purified from C. violaceum [Zinger-Yosovich, K., Sudakevitz, D., Imberty, A., Garber, N. C., and Gilboa-Garber, N. (2006) Microbiology 152, 457-463] and has been confirmed to be a tetramer with subunit size of 11.86 kDa and a binding preference for fucose. We describe here the cloning of CV-IIL and its expression as a recombinant protein. A complete structure-function characterization has been made in an effort to analyze the specificity and affinity of CV-IIL for fucose and mannose. Crystal structures of CV-IIL complexes with monosaccharides have yielded the molecular basis of the specificity. Each monomer contains two close calcium cations that mediate the binding of the monosaccharides, which occurs in different orientations for fucose and mannose. The thermodynamics of binding has been analyzed by titration microcalorimetry, giving dissociation constants of 1.7 and 19 microM for alpha-methyl fucoside and alpha-methyl mannoside, respectively. Further analysis demonstrated a strongly favorable entropy term that is unusual in carbohydrate binding. A comparison with both PA-IIL and RS-IIL, which have binding preferences for fucose and mannose, respectively, yielded insights into the monosaccharide specificity of this important class of soluble bacterial lectins.

Bacterial Proteins↗
PubMedDate not supplied

Increased activity of Chromobacterium viscosum lipase in aerosol OT reverse micelles in the presence of nonionic surfactants.

Modification of AOT reverse micellar systems with various alkyl glucosides and nonionic surfactants was attempted in order to improve the activity to Chromobacterium viscosum lipase. Tweens and Tritons, having the poly(oxyethylene) chain, have been shown to be solubilized at the oil-water interface of AOT micelles. Alkyl glucosides were also solubilized at the interface. These additives form mixed micelles with AOT and increase the concentration of the micelles. In contrast, Spans were found to be solubilized in the micro water pool of AOT micelles. Addition of nonionic surfactants decreased the hydrophobicity of the reverse micellar systems. Improvement of the lipase activity was achieved by the addition of nonionic surfactants, because of suppression of the hydrophobic and electrostatic interaction between AOT and lipase. The addition of nonionic surfactant having a poly(oxyethylene) chain has been shown to effectively increase the activity of the lipase in reverse micelles.

Chemical Phenomena↗
PubMed2001

Molecular basis for enantioselectivity of lipase from Chromobacterium viscosum toward the diesters of 2,3-dihydro-3-(4'-hydroxyphenyl)-1,1,3-trimethyl-1H-inden-5-ol.

2,3-Dihydro-3-(4'-hydroxyphenyl)-1,1,3-trimethyl-1H-inden-5-ol, 1, is a chiral bisphenol useful for preparation of polymers. Previous screening of commercial hydrolases identified lipase from Chromobacterium viscosum (CVL) as a highly regio- and enantioselective catalyst for hydrolysis of diesters of 1. The regioselectivity was > or =30:1 favoring the ester at the 5-position, while the enantioselectivity varied with acyl chain length, showing the highest enantioselectivity (E = 48 +/- 20 S) for the dibutanoate ester. In this paper, we use a combination of nonsymmetrical diesters and computer modeling to identify that the remote ester group controls the enantioselectivity. First, we prepared nonsymmetrical diesters of (+/-)-1 using another regioselective, but nonenantioselective, reaction. Lipase from Candida rugosa (CRL) showed the opposite regioselectivity (>30:1), allowing removal of the ester at the 4'-position (the remote ester in the CVL-catalyzed reaction). Regioselective hydrolysis of (+/-)-1-dibutanoate (150 g) gave (+/-)-1-5-dibutanoate (89 g, 71% yield). Acylation gave nonsymmetrical diesters that varied at the 4'-position. With no ester at the 4'-position, CVL showed no enantioselectivity, while hindered esters (3,3-dimethylbutanoate) reacted 20 times more slowly, but retained enantioselectivity (E = 22). These results indicate that the remote ester group can control the enantioselectivity. Computer modeling confirmed these results and provided molecular details. A model of a phosphonate transition state analogue fit easily in the active site of the open conformation of CVL. A large hydrophobic pocket tilts to one side above the catalytic machinery. The tilt permits the remote ester at the 4'-position of only the (S)-enantiomer to bind in this pocket. The butanoate ester fits and fills this pocket and shows high enantioselectivity. Both smaller and larger ester groups show low enantioselectivity because small ester groups cannot fill this pocket, while longer ester groups extend beyond the pocket. An improved large-scale resolution of 1-dibutanoate with CVL gave (R)-(+)-1-dibutanoate (269 g, 47% yield, 92% ee) and (S)-(-)-1-4'-monobutanoate (245 g, 52% yield, 89% ee). Methanolysis yielded (R)-(+)-1 (169 g, 40% overall yield, >97% ee) and (S)-(-)-1 (122 g, 36% overall yield, >96% ee).

Chromobacterium↗
PubMed2002

Chromobacterium violaceum infection: A rare but frequently fatal disease.

The authors report a rare case of Chromobacterium violaceum infection in a 2-month-old child. She presented with an apparently localized abscess, which appeared to respond well to therapy. However, the infection recurred later with a fulminant course. The organism frequently is dismissed as a contaminant or not identified properly, and the fatality rates are high. A high degree of awareness about this infection needs to be created, especially among pediatricians and pediatric surgeons, because children appear to be infected more commonly than adults, and aggressive therapy is needed to save these patients.

Abscess↗
PubMed2003

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability.

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) approximately 500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) widespread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications.

Adaptation, Physiological↗
PubMed1995

L-tryptophan 2',3'-oxidase from Chromobacterium violaceum. Substrate specificity and mechanistic implications.

L-Tryptophan 2',3'-oxidase, an amino acid alpha,beta-dehydrogenase isolated from Chromobacterium violaceum, catalyzes the formation of a double bond between the C alpha and C beta carbons of various tryptophan derivatives provided that they possess: (i) a L-enantiomeric configuration, (ii) an alpha-carbonyl group, and (iii) an unsubstituted and unmodified indole nucleus. Kinetic parameters were evaluated for a series of tryptophan analogues, providing information on the contribution of each chemical group to substrate binding. The stereochemistry of the dehydro product was determined to be a Z-configuration from proton nuclear magnetic resonance assignments. No reaction can be observed in the presence of other aromatic beta-substituted alanyl residues which behave neither as substrates nor as inhibitors and therefore do not compete against this reaction. The enzymatic synthesis of alpha,beta-dehydrotryptophanyl peptides from 5 to 24 residues was successfully achieved without side product formation, irrespective of the position of the tryptophan residue in the amino acid sequence. A reactional mechanism involving a direct alpha,beta-dehydrogenation of the tryptophan side chain is proposed.

Amino Acid Sequence↗
PubMed1998

Phenylalanine hydroxylase from Chromobacterium violaceum. Uncoupled oxidation of tetrahydropterin and the role of iron in hyroxylation.

A gene encoding phenylalanine hydroxylase has been cloned from Chromobacterium violaceum and expressed in Escherichia coli. The purified phenylalanine hydroxylase contains copper, which does not support enzymatic activity. Upon removal of copper by dithiothreitol (DTT), the enzyme contains substoichiometric amounts of calcium and zinc but little or no redox-active metal ions. The copper-depleted hydroxylase catalyzes the phenylalanine-dependent oxidation of 6, 7-dimethyltetrahydropterin (DMPH4) by O2 in a reaction in which phenylalanine is not hydroxylated and does not appear to undergo a chemical change, and hydrogen peroxide is produced. Analogs of phenylalanine also activate the oxidation of DMPH4. Both the copper-phenylalanine hydroxylase and the copper-depleted hydroxylase catalyze the hydroxylation of phenylalanine in the presence of DTT and FeSO4 in a reaction in which hydrogen peroxide is not produced. The apparent values of Km for Fe2+ and DTT are 0.28 microM and 1.1 mM, respectively, at 1.0 mM phenylalanine, 120 microM DMPH4 and pH 7. 4 and 23 degreesC. The apparent value of kcat is 14.3 s-1 under these conditions. Glutathione, mercaptoethanol, and dihydrolipoate support the hydroxylation of phenylalanine essentially as well as DTT. Incubation of copper-depleted hydroxylase with FeSO4, phenylalanine, and DTT followed by gel permeation chromatography leads to an iron-hydroxylase containing approximately 1 molecule of iron per molecule of enzyme. The iron-hydroxylase displays an optical absorption band extending from 300 to 600 nm, and it catalyzes the hydroxylation of phenylalanine at the same maximum rate as the iron-activated hydroxylase but does not require added Fe2+. We conclude that iron participates in the hydroxylation of phenylalanine. Iron is not required for the oxidation of DMPH4, although it may exert a modest acceleration effect. A hypothetical mechanism is presented wherein the reaction of iron with the putative 4a-hydroperoxy-DMPH4 leads to 4a-hydroxy-DMPH4 and a high valent iron-oxy species. The iron-oxy species is postulated to react with phenylalanine in the hydroxylation process.

Amino Acid Sequence↗
PubMed2001

Successful treatment of an infant with Chromobacterium violaceum sepsis.

Chromobacterium violaceum sepsis, a rarely reported phenomenon, has a high mortality rate. We report a unique case of C. violaceum sepsis in an infant. A 4-month-old girl presented to our institution with fever, pustular skin lesions, and distended abdomen, as well as diminished activity and mental status. Radiological investigation revealed brain, lung, and hepatic abscesses. The infant was successfully treated with trimethoprim-sulfamethoxazole and ciprofloxacin.

Anti-Bacterial Agents↗
PubMed1976

beta-Lactamase activity in Chromobacterium violaceum.

A strain of Chromobacterium violaceum isolated from a fatally infected patient was found to produce a beta-lactamase. When the organism was grown in drug-free medium, beta-lactamase activity was barely detectable, but when it was grown in the presence of penicillin G, a much larger amount of activity was produced. The beta lactamase was active primarily against cephalosporins; it was sensitive to inhibition by cloxacillin but resistant to p-chloromercuribenzoate. Thus this enzyme closely resembled the common type of beta-lactamase found in Pseudomonas aeruginosa. The organism was relatively susceptible to ticarcillin, carbenicillin, and cefoxitin, which resected hydrolysis by its beta-lactamase, but was quite resistant to 11 other beta-lactam antibiotics. Production of the beta-lactamase appeared to be mediated by chromosomal genes.

Cefoxitin↗
PubMed1977

Purification of lipase from Chromobacterium viscosum by chromatography on palmitoyl cellulose.

Palmitoyl cellulose was used to adsorb the extracellular lipase [triacylglycerol acyl-hydrolase EC 3.1.1.3] of Chromobacterium viscosum from crude enzyme solution, and the adsorbed enzyme was eluted with a suitable detergent, such as Adekatol 45-S-8 or Triton X-100. The enzyme was then purified by chromatography on a palmitoylated gauze column with an overall recovery of 71% and an increase in the specific activity of 11-fold from the supernatant fluid of bacterial cultures. Further purification procedures included fractionation with acetone, and chromatography on Sephadex G-150 and G-75 columns. Two isoenzymes were obtained, each in a homogeneous state on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis: one had a molecular weight of 120,000 and pI of 3.7 and the other a molecular weight of 30,000 with a pI of 7.3.

Cellulose↗
PubMed1978

Stimulation of Chromobacterium lipase activity and prevention of its adsorption to palmitoyl cellulose by hydrophobic binding of fatty acids.

Fatty acids prevented adsorption of purified Chromobacterium lipase [triacylglycerol acylhydrolase, EC 3.1.1.3] onto palmitoyl cellulose (Pal-C) and also increased the activity of the purified lipase. These effects increased with increase in the concentration and chainlength (up to 16 carbon atoms) of the fatty acids, and long-chain unsaturated fatty acids, such as oleic acid, linoleic acid and erucic acid, were most effective. When the lipase was adsorbed (immobilized) on Pal-C, its activity was elevated to 20 times that of the free lipase in detergent-free reaction mixture (olive oil-buffer system). Thus lipase was adsorbed to Pal-C through a hydrophobic site distinct from its catalytic site and the binding of fatty acids to the hydrophobic site seems to result in stimulation of the lipase activity.

Adsorption↗
PubMed2002

Chromobacterium violaceum: a case of diarrhea in Senegal.

A 5-year-old infant with diarrhea had heavy growth of Chromobacterium violaceum cultured from stool. This organism is restricted geographically between latitudes 35 degrees N and 35 degrees S. It can cause sepsis and various focal infections but is not a well-known cause of diarrhea.

Child, Preschool↗
PubMed2002

Chromobacterium violaceum infection in children: a case of fatal septicemia with nasopharyngeal abscess and literature review.

This previously healthy 5-year-old boy initially presented with fever and purulent conjunctivitis. The course evolved rapidly into preseptal and facial cellulitis, nasopharyngeal abscess and sepsis. Chromobacterium violaceum was isolated from conjunctival exudate and blood cultures. He received intravenous cefazolin therapy for 2 days, followed by penicillin, oxacillin and netilmicin. However, no improvement was noted, and he died on the fifth days of illness.

Abscess↗
PubMed1998

Chromobacterium violaceum infection.

Chromobacterium violaceum infection is confined to the tropical and subtropical areas, with almost all reported cases occurring in the Southeast. The most common feature of this infection is sepsis, followed by cutaneous involvement and liver abscesses. Treatment consists of surgical drainage of purulent collections and appropriate antimicrobial therapy, such as chloramphenicol, gentamicin, imipenem, trimethoprim-sulfamethoxazole, or ciprofloxacin. Although C violaceum infection is rare, it is potentially fatal and remains an important entity for clinicians to suspect and treat appropriately.

Anti-Bacterial Agents↗
PubMed2005

Invasive Chromobacterium violaceum infection in children: case report and review.

A 3.3-year-old boy developed Chromobacterium violaceum abscesses of lungs, liver and spleen and was successfully treated. He had chronic granulomatous disease (CGD). Twenty-five episodes of invasive C. violaceum infection in 24 children were reviewed. All 9 CGD and 10 nonbacteremic cases survived, but 12 of 16 (75%) non-CGD and 12 of 15 (80%) bacteremic patients died.

Abscess↗
PubMed1997

Quorum sensing and Chromobacterium violaceum: exploitation of violacein production and inhibition for the detection of N-acylhomoserine lactones.

Quorum sensing relies upon the interaction of a diffusible signal molecule with a transcriptional activator protein to couple gene expression with cell population density. In Gram-negative bacteria, such signal molecules are usually N-acylhomoserine lactones (AHLs) which differ in the structure of their N-acyl side chains. Chromobacterium violaceum, a Gram-negative bacterium commonly found in soil and water, produces the characteristic purple pigment violacein. Previously the authors described a violacein-negative, mini-Tn5 mutant of C. violaceum (CV026) in which pigment production can be restored by incubation with supernatants from the wild-type strain. To develop this mutant as a general biosensor for AHLs, the natural C. violaceum AHL molecule was first chemically characterized. By using solvent extraction, HPLC and mass spectrometry, a single AHL, N-hexanoyl-L-homoserine lactone (HHL), was identified in wild-type C. violaceum culture supernatants which was absent from CV026. Since the production of violacein constitutes a simple assay for the detection of AHLs, we explored the ability of CV026 to respond to a series of synthetic AHL and N-acylhomocysteine thiolactone (AHT) analogues. In CV026, violacein is inducible by all the AHL and AHT compounds evaluated with N-acyl side chains from C4 to C8 in length, with varying degrees of sensitivity. Although AHL compounds with N-acyl side chains from C10 to C14 are unable to induce violacein production, if an activating AHL (e.g. HHL) is incorporated into the agar, these long-chain AHLs can be detected by their ability to inhibit violacein production. The versatility of CV026 in facilitating detection of AHL mixtures extracted from culture supernatants and separated by thin-layer chromatography is also demonstrated. These simple bioassays employing CV026 thus greatly extend the ability to detect a wide spectrum of AHL signal molecules.

Chromobacterium↗