Biotransformation of Chloroaromatics: the Impact of Bioavailability and Substrate Specificity.

Biotransformation

of

Chloroaromatics: the

Impact

of

Bioavailability

and Substrate

Specificity

Demetrio

Randazzo

Marta

Ferraroni Andrea Scozzafava Ludmila

Golovleva

,

Fabrizio

Briganti

’*

Laboratorio di Chimica

Bioinorganica, Dipartimento

di Chimica, Universith diFirenze

2Skryabin

Institute

_of

Biochemistry and Physiology

of

Microorganisms

RAS

142290, Pushchino,

Moscow

region, Russia

ABSTRACT

The effect of surfactants on the biodegradation of mono-aromatic hydrocarbons such as benzene, chlorobenzene and 1,2-dichlorobenzene by an Escherichia coliJMI09(MI) recombinant strain, carrying a

gene cluster containing the genes for benzene dioxygenase, cis-benzene dihydrodiol dehydrogenase, and

catechol2,3-dioxygenasefrom Pseudomonasputida ML2, hasbeeninvestigated.

We observed that the efficiency of the benzene dioxygenase catalyzed conversions to cis-dihydrodiols depends on the balance among real substrate specificity, bioavailability, and toxicity effects of highly

concentrated aromatic hydrocarbons. The utilization of non ionic surfactants makes it possible to partly

overcomethe limiting stepofbiodegradationprocesses for scarcelywatersolublehydrocarbons hinderedby

their limitedbioavailability.

Furthermore the cis-benzene dihydrodiol dehydrogenase and the extradiol catechol 2,3-dioxygenase,

which inthepresently analyzedbiodegradativepathwayshouldfurtherdegradethepollutants, areknown,the first tobe selectively specific for the (lR,2R)-dihydrodiol derivative which is not produced bythe benzene

dioxygenase, thesecond, tobe dead-end inhibitedbythecorrespondingchlorinated catechois. Inthepresent example this results in the accumulation ofthe corresponding chlorinated cis-dihydrodiols which can be useful for asymmetricsynthesis.

On theotherhandthepracticalutilizationof thesystem forbioremediationpurposes requiresthe efficient

Towhomcorrespondenceshould be addressed:

Prof. Dr. FabrizioBriganti

Laboratorio di ChimicaBioinorganica,

DipartimentodiChimica,UniversitAdegliStudi diFirenze,

ViaDella Lastruccia3,50019, Firenze, Italia

Phone(+39)0554573343; FAX (+39)0554573333;

toI.

2,

Nos.

3-4, 2004

_{Biotran.’ormation}

_of

Chloroaromatics:the hnpact

_of

Bioavailabilily And Subso’ate SpecificiO,

conversionofthechlorinatedcatecholsbyspecific intradiol ring-cleaving dioxygenases, thecrystalstructures of some of these last enzymes are currently under analysis in our laboratory to understand the structural-functional correlations. Preliminary data show overallstructures similar tothecatechol 1,2-dioxygenase from

Acinetobactersp. ADP1 thus suggesting that the substrate specificitydifferences are mainlyrelatedtosubtle differencesinthe catalyticsite.

Keywords: Benzene,

Chlorobenzene, 1,2-dichlorobenzene, Benzene dioxygenase, Surfactants, Direct

micellar

systems,Biodegradation, Biotransformation.

INTRODUCTION

Remediative or synthetic technologies based on microbial traiJformations of hydrocarbons (biotransformations

hereafter)

are becoming everydaymore relevant. In particular in situ processes forthe removal of pollutingaromatic hydrocarbonscanpotentially benefit ofthe capabilities of enzymatic systems

in terms of faster and gentle treatment conditions, reduced environmental pollution, and low costs /1,2/. Furthermore environmentallybenign procedures utilizing such enzymes have interestingapplications forthe synthesis of usefulchemicals/3-7/.

The aerobic biotransformation ofaromatic hydrocarbons always require the action ofoxygenases, often containing iron ions essential for the catalysis of the aromatic ring hydroxylation and the consecutive ring opening/8,9/.Inbioproductionprocesseshowever the useof isolatedenzymesis not realisticmainlybecause

hydroxylating oxygenases areunstable multi-component systems difficult to purify

and

requiring expensive co-substrates/10,11/. Therefore technologies using whole cells engineered microorganisms which provide for the over-expression of such enzymatic systems havebeendeveloped/12, 13/.

Pseudomonas putida ML2, amicroorganismfirst described in 1973, isabletoutilize benzeneasthe sole

carbon and energy source/14/. This bacterium oxidizes benzene to cis-l,2-dihydroxy-cyclohexa-3,5-diene (cis-benzene dihydrodioi) throughthe addition of both atoms ofdioxygen tothe aromatic nucleus(reaction catalyzed by benzene 1,2-dioxygenase, (BDO)). Afterwards the product is oxidized to catechol by a

cis-dihydrodiol dehydrogenase

(BCD).

Finally catechol is further converted through oxygenative ring cleaving by catechol 2,3-dioxygenase (C2,30)to a-hydroxymuconic semialdehydewhich aftera fewreactions enters

theregularcarbon cycle(seeScheme 1)/I5-18/.

COOH

N D*

_\OH

NAD NADH OH _CHO

+H H +H

BDO

BCD

C2,30

DemetrioRandazzoetal. BioinorganicChem&try and Applications

Oneof themaindrawbacksin biotransformationprocessesof aromatichydrocarbons isgenerallythevery

low rate ofcatalysis due to a variety of factors such as the scarce mass transfer rate ofthe hydrophobic substrates, the restricted enzymatic substrate specificity,andthe toxicity effects exerted by such compounds

onmicro-organisms/12/.

In the present work we will mainly focus on bioavailability limitations to efficient biotransformation procedures, briefly mentioning the aspect of enzymatic specificity for chlorobenzenes.

Regardingbioavailability two-phase systems (like water/organic

solvents)

in whichthe major component

is an organic solventable to solubilize iarg quantities of thehydrophobic pollutants havebeen formulated, the major drawbackbeing thatfrequently the cell viability is fairly reduced afteronlyfewhours duetothe

toxiceffectsofthe organicphase/19,20].

Living systems accomplish high levels of selectivity and efficiency using compartmentalization through self assembling systems oftencomposed byamphiphatic unitssimilar tothose of synthetic surfactantswhich form micellar systems above the critical micellar concentration /21-23/. Direct micelles are capable to solubilize amounts ofapolar compounds in theircore/24-26/. Such systems can be regarded as chemical

microreactors, where hydrophobic substances stored in the apolar center can diffuse to the hydrophilic aqueousmedium ordirectlytothe adjoining cellmembranes/27/.

Micellarphases in microbial bioconversions have been observed to be milderthan vigorous mixing of multiphasic media, and the effective improvement ofconversion kinetics has been investigated into details for polyaromatic hydrocarbons /28-31/. In such cases high substrate conversion rates and yields were

observed togetherwithhigh cellviabilities.

Regarding enzyme specificity we can remark that the removal ofcontaminant mixtures from polluted environments is particularly challenging. In fact mixtures of halogenated and alkylated aromatic hydrocarbons are widely spread pollutants and generallythe degradation pathways for haloaromatics differ

considerably from those of the alkyl-substituted analogues. In particular the ring cleaving dioxygenases

involved inthetransformationofalkyl-aromaticsaregenerallyoftheextradioltype whereasthoseimplicated

in the cleavage ofhalogenated aromatics belong to the intradiol class. Strict substrate specificities are also

observed among enzymes belonging to the same class of dioxygenases. Only one exception ofextradiol

cleaving dioxygenase abletocatalizethecleavageofhaloaromaticshas beenrecentlyobserved/32-34/. The understanding of the structural factors which cause the observed enzymatic specificities has to be regardedascrucial forthe design ofmoreefficientbioremediationtechniques.

In the present paper the influence of bioavailability onthe efficiency of biotransformation processes for

aromatic hydrocarbons like benzene and chloroaromatics like chlorobenzene and 1,2-dichlorobenzene is examined.

The data clearly show reduced affinities ofthe benzene dioxygenase for the chlorinated compounds although the presence of micellar systems contributes to increase the transformation rates and yields.

Anyway

thesurfactantdoes notallowtochange the real substrate specificities andtoprevent theinactivation ofthe extradio! ring cleaving dioxygenases, it isknown that the normal intradiol catechol dioxygenasesare unable to cleave chlorocatechols; therefore we have started to determine the x-ray structures of some

Vol.2, Nos. 3-4, 2004

_{Biotran.brmation of}

Chloroaromatics: the hnpact

_of

Bioavailability And SubstrateSpecificiO

intradiol dioxygenases specializing in the cleavage of 4-chlorocatechol and hydroxyquinol to reveal the

factors essentialfor substrate selectivity.

EXPERIMENTAL Materials

Triton XI00, benzene, chlorobenzene and 1,2-chlorobenzene, werepurchased from Sigma-Aldrich S.r.1. (Milan, Italy). Water was purified in a reverse osmosis Milli-Ro system and subsequently treated with a

Milli-Q system (Millipore). All theother chemicals wereofthe bestpurityavailable.

Microorganisms

The E. coli

JMI09(MI)

recombinant strain carrying benzene dioxygenase where DNA shuffling was appliedto bedCl gene(reductase

component),

cis-benzenedihydrodiol dehydrogenase, and the catechol 2,3-dioxygenase cloned from Pseudomonas putida ML2 was used for the biodegradation studies and kindly suppliedby Dr. J.R. Mason (King’s College, London, UK). Such abiological system isabletocatalyze the

conversion of benzene and other aromatic compounds to the corresponding semialdehydes as previously reported 14-16/.

Culturemediaandconditions

E. coli inocula were initially grown in LB medium plus ampicillin 100 g/ml for 8-12 hours then transferredto M9 medium additioned with succinate 20mMandtheappropriate surfactant under standingor

stirringconditions at30C/35/. Theexpression ofthedioxygenases clusterwasconstitutive.

Viabilityexperiments were performedby platingestimated amounts ofcells, obtainedafter dilution with

LB medium, on

LB-agar

plates. After 12-18hours incubation at30Cthe grown colonies, correspondingto the viablecells,were

manualiy

counted.

Bioconversion experiments were performed at 30C, 100-200 rpm orbital shaking, adding to fresh M9 medium with the appropriate concentrations of surfactant, oil, hydrocarbon, and 1.6x l09 cells/ml

correspondingtoabout 60-80Units/literofbenzene dioxygenase activity.

One unit ofdioxygenase activity isdefined as the amountofcells producing

_mol

of 1,2-dihydro-l,2-dihydroxybenzenein rainunderthetestconditions.

HPLC

determination ofbioconversions kinetics

Reverse phase C18 columns (4.6 x 150 mm) connected to a Waters HPLCAlliance 2690 anda Waters 996 photodiode array detector(Milford,

MA,

U.S.A.)both interfacedtopersonalcomputerswereused under

DemetrioRandazzoetal.. Bioinorganic Chemistry and Applications

the reaction mixtures. 5-20

_tl

samples were injected after 3’ centrifugation at 14,000 rpm and 4C. The absorbance of the eluate was monitored between 200 and 600 nm. The concentrations ofcompounds at differenttimes during the kineticrunshave beendeterminedfrom theareas of thecorresponding peaks. All experimentswere carriedoutinduplicateand the valuesreportedare means.

Analysis of Bioconversion Products

The products generated bythe bioconversions ofbenzene,toluene and ethylbenzene catalyzed bythe E.

coli

JM109(MI)

recombinant strain carrying the genes cluster cloned from P. putida ML2 were analyzed using LC-MSand UV-Visspectroscopytechniques.

Forthe liquid chromatography-mass

(LC-MS)

experiments, a Micromass/Waters ZMD2000quadrupole system, connectedto aWatersAlliance2690HPLCwasused(Milford,

MA,

U.S.A.).Themassspectrometer

was calibratedusing

NaCsl2.

Amass range of 20-300 amuwas scannedand the datawere acquiredwiththe

MassLynx

NT3.5 data system.

UV-Vis

Spectroscopy

UVmeasurements were carried out ondouble beamVarian

Cary

3 spectrophotometers using 1.0-0.1 cm

pathlength Hellma 110 quartz suprasil cells.

RESULTSAND DISCUSSION

The cluster ofenzymes: benzene dioxygenase, cis-benzene dihydrodiol dehydrogenase, andthe catechol 2,3-dioxygenase cloned from Pseudomonas putida ML2, utilized in the present investigation, is known to convert benzene and, with lower efficiencies, other substituted monocyclic aromatic hydrocarbons to the correspondingsemialdehydes/14-16/.

To increase the efficiency of the system under investigation DNA shuffling experiments on the bedCl gene (reductasecomponent) ofBDO made itpossibleto obtain the present clone which shows an enhanced catalytic activity towards benzeneconversion to the corresponding semialdehyde

(250-300

% enhancement

was observed with respectto the native system) (personal communication, Dr. J.R. Mason, King’s College, London, UK) 14-16/.

With the exception ofbenzene, the solubility ofwhich is around 23

mM

in water systems at 20C, the

limited solubilities ofthe other substrates tested in water media

(see

Table 1) could not allow optimal

conversion rates. Possible approaches to more efficient biotransformation processes could employ a two

phase system butthecontactareabetweenthe twophaseswhichshould influence the substratetransferrate is scarce even under vigorous stirring /19, 20/. A much higher contact surface can be obtained in

micro-compartmentalized media, wherethehydrophobic substrates aredispersed downto nanometer sizeddroplets

Vol. 2, Nos. 3-4, 2004 _{Biotram)rmation}

_of

Chloroaromatics:the hnpact

_{ofBioavailabili}

And SubstrateSpecO%i.

Table

Solubilitiesfor the differentaromaticcompoundsinthemediatested inthe present work

Substrate Benzene chloro-benzene 1,2-dichioro-benzene SolubilityinWater

2.24xlOZM

4.14x10-3M

.6.80x

104M

Solubilityin M9/TritonX100 1.5% >5.0x

02M

> I.Oxl

O’2M

>0.5x

O’2M

Dilute direct micellar systems made using suitable non-ionic surfactants can increase the hydrophobic substrate solubility and provide a less aggressiveenvironmentforbacterial cells/27-31/. Forthis reason we utilized 1.5% v/v of non-ionic Triton XI00(R) (t-octylphenoxypolyethoxyethanol) in the mineral culture

medium

(M9)

for the E. coli straincontaining the genes forthe overexpression of thebenzene dioxygenase cluster(seeExperimental).

Ageneral property of

_L

micellarsolutions is theirabilityto solubilize a certain amount ofhydrophobic

additives. It has been reported that the solute localization in the micellar micro-compartment is directly relatedto itshydrophobicity,sothatthemorepolarorpolarizablecompoundssuchasaromatichydrocarbons

arepreferentially foundinthe so called palisadelayerwheretheyinteract withthepolar group/21,22/.

Previous studies on microemulsion systems showed that higher apparent solubilities for polyaromatic hydrocarbonsprovided higherconversion ratesand yields/28-31/.

The bacterial strain viabilities in selected surfactant modified media were tested under stirring and

standingconditionsand providedevidenceof optimal growthenvironments/28].

As expected on the basis of benzene water solubility, the addition of Triton X100 1.5% to the

bioconversion environment forsuch substratedid notprovideany further improvementin masstransferrates andthereforethe conversion rates andyieldswere not enhanced(datanotshown).

In such micellar solutions it was possibletoraisethe real benzene concentration even above 50 mM but increasing the substrate concentration from 10 to 20 and to 40mM resulted in substantial reductions ofthe conversion rates duetotoxicity problems (see Figure 1). It isknownthat the addition of benzene and other

mono-aromatic hydrocarbons to the culture medium yields the accumulation of such compounds in the hydrophobic segment of the bacterial membrane causing an increased permeability of the cytoplasmic membrane and resulting in impaired bacterial growth due to metabolic energy losses and macromolecules leakage/36-38/. Consequentlythe final conversionyield that for 10mM (and lower concentrations) benzene

DemetrioRandazzoetal. BioinorganicChemistry and Applications

concentration was 100% was reduced to about 80 % and 65 % for 20 and 40 mM starting benzene

concentrationrespectively. 6

E

o 5

=

4

o

3 "o ₂

o

0 100 200 300 400 Time

_(minutes)

Fig. I" Time-dependentbioconversions ofdifferent concentrationsofBenzenein micellar systems of 1.5%

v/vTriton X100 in M9(startingconcentrations 10mM (e), 20 mM

(O),

or40mM

(’)

benzene). Thefinal cell concentrationof the inducedE. coliJM109(MI)recombinant strainresultedtobe 1.6 x

109

cells/ml.The kinetics were run at 30C and 140rpm.

Inordertopreventmetabolicenergy losseswetried tofurther add mM NADHor 10mMethanoltothe

culturemediumbutthis did notshowanyappreciable effectontheconversionprocessratesandfinalyields. Theconversion kinetics for chlorobenzene in M9 minimal medium andTritonXI00/M9solutions (1.5%

w/winsurfactant)are illustrated inFigure 2. Contrarilytowhat wasobserved forbenzene,the addition of the non ionic surfactant produces enhancements of the overall conversion rates at 5 mM initial substrate

concentration and afour-foldincrease of the finalyield. As in the case of benzene thedoublingof the initial concentration for the aromatic hydrocarbon (inthis casefrom 5 to 10 mM)causes substantial reductions of thecatalytic ratesduetothetoxiceffectsof such substrate(datanotshown).

Vol.2,Nos. 3-4, 2004

_{Biotransformation of}

C,hloroaromatics: the

Impact

_of

Bioavailability AndSubstrateSpecificity

E

2.0 o 1.0 0 0.5 0.0 0 200 400 600 800 1000 1200 1400 Time

(minutes)

Fig. 2: Time-dependentbioconversionsof5mM chlorobenzene inacqueousM9

(e)

or in micellarsystems containing of 1.5%v/v Triton X100 in M9

(O).

The final cell concentration of the induced E. coli

9

JM109(MI) recombinant strainresulted to be 1.6 x 10 cells/ml. The kinetics wererun at 30C and

160 rpm.

LC-MS experiments allowed us to confirm and quantify the products ofchlorobenzene conversion. As observed in scheme II the action of benzene 1,2-dioxygenase on chlorobenzene results mainly in the formation of 1S,2S-3-chloro-cis-l,2-dihydroxy-l,2-dihydrocyclohexa-3,5-diene which is not further

converted into the corresponding catechol or semialdehyde due to the specificity limitations of the

corresponding cis-benzene dihydrodiol dehydrogenase, and catechol 2,3-dioxygenase from Pseudomonas

putida ML2 /39,40]. In fact a recent study showed that the presently investigated cis-benzene dihydrodiol dehydrogenase is not able toconvert (1S,2S)-3-chloro-cis-l,2-dihydroxy- 1,2-dihydrocyclohexa-3,5-diene to

theresulting catechol since ithas a selectivepreferencefor the(IR,2R)enantiomer which isnotproduced by

BDO/41/.

The formation of traces(<0.2%)of2-chloro-phenolprobablyadecompositionproductof thestartingdiol has also been observed. In table 2 are reported the results ofproducts quantification for chlorobenzene conversion in the different media.

DemetrioRandazzoetal. BiohorganicChemisoyandApplications

Cl Cl

SchemeII

Similarresultswereobtainedanalyzingthe 1,2-dichlorobenzene conversion. In Figure3 arereportedthe

conversion kinetics for 1,2-dichlorobenzene at 5 mM initial concentration with or without the addition of TritonXl00 1.5%w/wtotheM9 medium.Theadditionofthesurfactant supportsamore efficient conversion of 1,2-dichlorobenzene due to the increased substrate bioavailability, resulting in a six-fold final yield

increase.

Also in the case of 1,2-dichlorobenzene the substrate specificity of benzene 1,2-dioxygenase drives

towards the formation of 3,4-dichloro-cis-1,2-dihydroxy- 1,2-dihydrocyclohexa-3,5-dienethataccumulates in

Cl Cl

Cl H

OH H

H the reaction environment(Table2)/42/:

Cl

Cl ,OH

OH SchemeI11

Microemulsionsobtained by 1%ethyloleate addition tothemicellarsystemswhich had been previously

utilized to further increase substrate bioavailability did not shown any additional enhancement in the

conversion ratesandyieldsof 1,2-dichlorobenzene(Figure 3, Table2)/28-30/.

In conclusion the utilization of direct micellar systems able to solubilize aromatic hydrocarbons at high

concentrations canallow improvementtoa certain extentof the efficiency ofbiotransformationprocesses by increasing substrate transferrates. The present study has also allowed it tobe determinedthat the apparent

loweraffinityofBDOfor chloro-benzene and 1,2-dichloro-benzene than forbenzene can bepartlyovercome in micellar systems where the utilization ofsuitable surfactants can considerably improve the mass transfer

rates andconsequently thefinalproduct yields.

Furthermore the stringent selectivitiesof BCD and C2,30 causetheaccumulation ofsignificantamounts ofinterestingchiraisynthonsthat are known tobe usefulfor fine chemicalsproduction/3-7,43/.

Vol.2, Nos. 3-4, 2004

_{Biotransformation}

_of

Chloroaromatics: the

Impact

_of

Bioavailability And Substrate Specificity

0.5 0.4 0 0.:3 0 ( 0.2 0 200 400 600 800 1000 1200 1400 1600 Time(minutes)

Fig.3" Time-dependent bioconversions of5 mM 1,2-dichlorobenzene in acqueous M9

()

or in micellar

systems containingof 1.5%v/vTriton X100 in M9

(O)

or 1.5%v/vTritonXI00/1%Ethyl Oleate in M9

(’).

The final cell concentration of the induced E. coli JMI09(MI) recombinant strain resulted tobe 1.6 x

109

cells/ml. Thekinetics wererun at 30C and 160rpm.

Table2

Productsobtainedfromchlorobenzene and 1,2-dichlorobenzenebiotransformationsby the BDOenzymes clusterin differentculturemedia.(Starting substrateconcentration 5raM)

SUBSTRATES MEDIUM chloro-benzene 1,2-dichloro-benzene M9 M9/TritonX100 1,5% 10.2% 41.2% M9 1.5% M9/TritonX100 1,5% 9.3% 0 M9/TritonX100 1,5A/Ethyl Oleate 1% 8.6% PRODUCTS YIELDS 3-chloro-cis- dihydroxy- 1,2- dihydrocyclohexa-3,5-diene 3,4-dichloro-cis- dihydroxy- 1,2- dihydrocyciohexa-3,5-diene

DemetrioRandazzoet

aL

BioinorganicChemistry and Applications

The formation and accumulation of intermediates during the biodegradation of aromatic hydrocarbons

also have implications in the treatment ofcontaminated waters and gases. In fact many of the observed intermediates are toxic tohumans and other organisms in the environmentand furthermore such catabolites contain mostof theinitialCOD(chemical oxygendemand)and all of thedissolvedorganic carbon

(DOC)

of the original compounds. Therefore the treatment of the aromatic hydrocarbons contamination results to be successfulonly when the intermediatesarealsoremoved/44,45/.

The limitations in biodegradative capacities of different bacteria are mainly due to the presence and nature of the substituents on the dihydroxybenzene ring. Whereas the unsubstituted catechol can be transformed via all pathways, methylated catechois derived from most natural and non-halogenated compounds are assimilated by the meta-cleavage pathway only /46,47/. Unfortunately meta-cleavage dioxygenases as the abovereported C2,30 from P. putida ML2 are rapidly inactivatedby chlorocatechols

due to the formationofreactiveacylchlorides; therefore such classes ofcompoundsaretypicallycatabolized

via the modified ortho-cleavage pathway which on the other hand.is not suitable for methyl-substituted

aromatics duetothe formation of dead-endmethyl-lactones/39,40,48,49/. The simultaneousbiodegradation ofchloro- and methyl-substituted aromatics often presentas mixtures at contaminatedsites is possible only by particularbacterial consortia orofparticularbacterial strains such as theP. putida GJ31 whichcontains an

unusualmeta-cleavagedioxygenase ableto convertchlorocatechols/32-34].

As mentioned above, intradiol dioxygenases have crucial roles in the modified ortho-cleavage pathway for the biotransformation ofhalogenated aromatics. Until now only the

X-ray

structures ofa few intradiol

dioxygenases have been determined showing large differences in oligomeric structures and sequence homologies/50-55/. These data, together with the information obtained through XAS experiments, are not sufficient to establish therolesof theactive site residues insubstrateselectivity/56/.

X-ray

diffraction studies are inprogressin ourlaboratory foranumber ofintradiol dioxygenasesinvolved in haiogenatedaromatic catabolism with different substrate specificities:thehydroxyquinol 1,2-dioxygenase

from Nocardioides simplex 3E, the 4-chlorocatechol dioxygenase and the 3-chlorocatechol 1,2-dioxygenaseboth from Rhodococcus opacus CP/57-59/. Inparticularstudies on the twochlorocatechol

1,2-dioxygenases involved respectively in the degradation pathways for 4-chlorophenol

(4-chlorocatechol

1,2-dioxygenase) and 2-chlorophenol

(3-chlorocatechol

1,2-dioxygenase) from Rhodococcus opacus CP

ascertainedthatthese enzymesdiffersignificantlyintheir catalyticproperties/60,61/.

Our preliminary analysis ofthe x-ray data shows that the overall crystal structures oftheseenzymes are

very similar to that of the catechol 1,2-dioxygenase from Acinetobacter Sp. ADPI in terms of quaternary

structure arrangements, molecular domains and active sitepositioning (see Figure 4 forhydroxyquinol

1,2-dioxygenase from Nocardioides simplex 3E, and 4-chlorocatechol 1,2-dioxygenase from Rhodococcus opacus CP) /62/. The refined three-dimensional structures of these enzymes with different substrate

specificitieswill provide details on the influence ofthe active site conformation andaminoacid substitutions

involved insubstrate selectivity and it willalsofurther improve theknowledgeofthecatalytic mechanism of

thisclassofdioxygenases.

Only a multidisciplinary approach investigating substrate bioavailability, enzyme specificity and efficiency

Vol. 2, Nos. 3-4,2004

_{Biotransformation}

(’Chloroaromatics:the

Impact

_of

Bioavailability AndSubstrateSpeclTcity

characterizations willallowto positivelyanswer to the everydaymoredemanding requestsof bioremediative andbiosynthetic technologies.

A

B

Fig. 4: Schematic overviews of the quaternary structures of 4-chlorocatechol 1,2-dioxygenase from

Rhodococcus opacus CP (A) and hydroxyquinol 1,2-dioxygenase from Nocardioides simplex 3E

DemetrioRandazzoetal.

_Bioino2eanic

Chemistryand Applications

ACKNOWLEDGEMENTS

We thank Dr. J.R. Mason forhelpful discussions. Weacknowledge the financial support ofthe COFIN 2002 Ministero deli’Universith e della Ricerca Scientifica e Tecnologica and the

Progetto

Finalizzato

Biotecnologie C.N.R.; we also acknowledge the support ofthe European Commission RTD Programme INCO-Copernicus grantECICA2-CT-2000-10006.

REFERENCES

1. R.L. Crawford and D.L. Crawford eds. Bioremediation: Principles and Applications, New.York, Cambridge Press (1996).

2. L.Y.

Young

and C.E Cerniglia, Microbial

_{Transformation}

and Degradation

of

Toxic Organic

Chemicals,New York,Wiley-Liss(I 995).

3. D.T.GibsonandR.E.Parales, Curr. Opin. Biotechnol., 1,236(2000).

4. T. Hudlicky,D.GonzalezandD.T.Gibson,AldrichirnicaActa,32,35 (1999).

5. T. Hudlicky and J.W. Reed, in Advances inAsymmetric Synthesis, A. Hassner, editor, JAI Press Inc. Greenwich,Connecticut

(1995).

6. G.N. Sheldrake, in:.Chirality inIndustry: TheCommercial

_Manufacture

and Applications

of

Optically

Active Compounds, A.N. Collins, G.N. Sheldrake and J. Crosby (Eds.), John Wiley & Sons Ltd., Chichester,UK, 127

(1992).

7. D.R. Boyd, N.D. Sharma,andC.C.R. Allen,Curr. Opin. Biotechnol., 12,564(2001).

8. A.L. FeigandS.J. Lippard,Chem. Rev.,94,759(1994).

9. S.

Harayama,

M.Kok, andE.L.Neidle,Annu. Rev. Microbiol., 46,565(1992).

10. J.R.MasonandR. Cammack,Annu. Rev.Microbiol. 46,277(1992).

11. S. Dagley,in: TheBacteria,J.R. Sokatch(Ed.),Academic Press,London,vol. !0, 527

(1986).

12. W.A. Duetz, J.B.vanBeilen,andB.Witholt,Curr. Opin. Biotechnol., 12, 419(2001).

13. K.N.TimmisandD.H. Pieper, Trends Biotechnol., 17, 201 (1999).

14. B.C. Axcell andP.J. Geary,Biochem.J., 136, 927(1973).

15. B.C.Axcell and P.J.

Geary,

Biochem. J.,146, 173 (1975).

16. M. ZamanianandJ.R.

Mason,

Biochem.J.,244,611

(1987).

17. J.R. Masonand P.J. Geary,Meth. Enzymol., 188, 134(1990).

18. C.S.Butler andJ.R. Mason,Adv. MicrobialPhysiol.,38,47 (1996).

19. S.Boeren, C. Laane,andR. Hilhorst, inBiocatalysis inOrganic Media,C. Laane, J.TramperandL.D. Lilly(Eds.),Elsevier Science Publishers B.V.Amsterdam,(1987).

20. O. Favre-Bulle, T. Schouten,J.Kingma,andB. Witholt, Bio/Technology9, 367(199I).

21. M. Bender (Ed.),

Interfacial

Phenomena in Biological Systems, Surfactant Science Series, Vol. 39, Marcel Dekker,lnc,NewYork,(199 I).

Vol. 2. Nos. 3-4, 2004

_{Biotransformation}

_of

Chloroaromatics: the

Impact

_of

Bioavailability And Substrate Specificity Technology Meet, VCHPublishers,New York, chapter4,

(1994).

23. G.J.SalterandD.B. Kell,Crit. Rev. Biotechnol. 15, 139

(1995).

24. S. D. Christian and J. F. Scamehorn (Eds.), Solubilization in

_Surfactant

Aggregates,

Marcel Dekker, New York, NY(1995).

25. P.C. Hiemenz and R. Rajagopalan Principles

of

Colloidand

_Surface

Chemistry, 3 rd Edition, Marcel

Dekker,Inc. NewYork, chapter8,(1997).

26. R. Nagarajan, Curt. Opin. Coll.

_Interface

Sci. 1,391 (1996).

27. F. Volkering,A.M. BreureandW.H. Rulkens,Biodegradation 8,401 (1998).

28. F. Briganti, D. Randazzo, A. Scozzafava, D. Berti, P. Baglioni,P.Di Gennaro, E.Galliand G. Bestetti, J. Mol. Catal. B 7,263(1999).

29. D. Berti, D. Randazzo, F. Briganti, P. Baglioni, A. Scozzafava, P. Di Gennaro, E. Galli and G.

Bestetti,J.

Inorg.

Biochem. 79, 103

(2000).

30. D. Randazzo, D. Berti, F. Briganti, A. Scozzafava, P. Baglioni. G. Bestetti, P. Di Gennaro and E. Galli,Biotech. andBioengin. 74:240(2001).

31. D. Berti, D. Randazzo, F. Briganti, A. Scozzafava, P.Di Gennaro, E. Galli, G.Bestetti and P. Baglioni,

Langmuir, 18, 6015 (2002).

32. A.E.

Mars,

T. Kasberg,S.R. Kaschabek, M. H.van

Agteren,

D.B.JanssenandW.Reineke,J. Bacteriol.

179,4530(1997).

33. S.R. Kaschabek, T. Kasberg, D. Muller, A.E. Mars, D.B. Janssen and W. Reineke, J. Bacteriol. 180,

296(1998).

34. A.E.

Mars,

J. Kingma, S.R. Kaschabek, W. ReinekeandD.B.Janssen, J. Bacteriol. 181, 1309

(1999).

35. J. Sambrook, E.F. Fritsch and T. Maniatis, Molecular Cloning- A Laboratory Manual, Cold Spring

Harbor Laboratory,PressCold SpringHarbor, NY. (1989).

36. J.Sikkema,J.A.M.deBontandB. Poolman, J. Biol. Chem.,269,8022

(1994).

37. J. Sikkema,J.A.M. deBontandB. Poolman,Microbiol. Rev.,59, 201 (1995).

38. B. AngelovaandH.-P. Schmauder, J. Biotechnol., 67, 13

(1999).

39. G.M. KleckaandD.T.Gibson,Appl. Env. Microbiol.,41, 1159(1981).

40. I. Bartels, H.-J.Knackmuss andW.Reineke,Appl. Environ. Microbiol. 47, 500

(1984).

41. C.C.R. Allen, C.E. Walker, N.D. Sharma,N.A. Kerley, D.R. Boyd and H. Dalton, Biocatal. Biotranlf., 20,257(2002).

42. S. Beil,J.R.Mason, K.N.TimmisandD.H.Pieper, J. Bacteriol., 180,5520(1998).

43. D.R.BoydandG.N.Sheldrake, Nat. Prod.

Rep.

15,309(1998).

43. J.E.T. van Hylckama Vlieg, G.J. Poelarends, A.E. Mars and D.B. Janssen, Curr. Opin. Microbiol., 3,

257(2000).

44. S.Fetzner, Appl. Microbiol. Biotechnol., 50,633 (1998).

45. W. Reineke, in Biological Degradation andBioremediation

_of

Toxic Chemicals, G.R. Chaudhry ed.. Portland,Oregon,Dioscorides Press,416(1994).

46. W. Reineke,Annu. Rev. Microbiol.,52,287(1998).

Demetrio Randazzoetal. BioinorganicChemistryandApplications

48. W.ReinekeamdH.-J. Knackmuss,Annu. Rev. Microbiol., 42,263 (1988).

49. L. Que Jr.andR.Y.N. Ho,Chem. Rev. 96,2607

(1996).

50. T.D.H.

Bugg

andC.J.Winfield, Nat. Prod.

Rep.

15,513

(1998).

51. L. Que, Jr., in: E.C.Theil, G.L. EichhornandL.G.Marzilli(Eds.),AdvancesinInorganicBiochemistry,

vol.

;:

IronBindingProteinswithout

_Cofactors

or

_Sulfur

Clusters. Elsevier, New York, 167 (1983).

52. T.E. Elgren, A.M. Orville, K.A. Kelly, J.D. Lipscomb, D.H. Ohlendorfand L. Que, Jr. Biochemistry,

36, 11504(1997).

53. D.H. Ohlendorf,A.M.OrvilleandJ.D. Lipscomb,J. Mol. Biol., 244,586(1994). 54. A.M.Orville,J.D. Lipscomb andD.H. Ohlendorf,Biochemistry, 36, 10052

(1997).

55. F. Briganti, S. Mangani,L. Pedocchi,A. Scozzafava,L.A. Golovleva,A.P. Jadanand l.P. Solyanikova, FEBSLett. 433,58(! 998).

56. M. Benvenuti, F. Briganti, A. Scozzafava, L.A. Golovleva, V.M. Travkin and S. Mangani, Acta Crystallogr. DBiol. Crystallogr. 55,901 (1999).

57. M. Ferraroni, M.Y. Ruiz Tarifa,.F. Briganti, A. Scozzafava, S. Mangani, I.P. Solyanikova, M.P. KolomytsevaandL.A.Golovleva,;4ctaCrystallogr. DBiol. Crystallogr. 58, 1074(2002).

58. M. Ferraroni, M Y Ruiz Tarifa, A Scozzafava, P. Solyanikova, M P. Kolomytseva, L.A. Golovleva

and F BrigantiActaCrystallogr. DBiol. Crystallogr., 59, 188(2003).

59. O.V. Maltseva, I.P. SolyanikovaandL.A.Golovleva,Eur. J. Biochem.226, 1053

(1994).

60. O.V. Moisseeva, O.V. Belova, I.P. Solyanikova, M. Schlomann and L.A. Golovleva, Biochemistry (Mosc)66,548(2001).

61. M.W.VettingandD.H.Ohlendorf, Structure FoldDes.,39,429(2000).