AntioxidantEnzymes

Leilei ZhangFlorianSchoberYuxiang ZhuDanielleScott

VeronicaCostiniti

Outline

• Superoxidedismutase(SODs)• Catalases• Peroxiredoxins• Glutathioneperoxidase

(Borgstahl GE, 1996; Miller AF, 2012)

Superoxide dismutase (SOD)

Superoxide dismutase (SODs) is an enzyme that catalyzes the dismutation of the superoxide (O2

−) radical into either ordinary molecular oxygen (O2) or hydrogen peroxide (H2O2).

There are three major families of superoxide dismutase, depending on the protein fold and the metal cofactor. In prokaryotes, genes are named by SodA, B, C; In eukaryotes, genes are named by Sod1, 2, 3.

Structure of a human Mn superoxide dismutase 2 tetramer.

Organism Gene/Product Localization

E. coli SodA/Mn-SOD Cytosol

SodB/Fe-SOD Inner membrane

SodC/Cu, Zn-SOD Periplasm

B. subtilis SodA/Mn-SOD Cytosol

S. cerevisiae Sod1/Cu, Zn-SOD Cytosol

Sod2/Mn-SOD Mitochondrial matrix

Human Sod1/Cu, Zn-SOD Cytosol

Sod2/Mn-SOD Mitochondria

Sod3/ExtracellularCu, Zn-SOD

Extracellular space

(Miller AF, 2012; Inaoka T et al, 1998; Park J et al, 1998)

SOD Genes

SOD’s Overall Reaction

Tohru Fukai,etal.Antioxidants&RedoxSignaling.2011

Lennicke etal.Cell CommunicationandSignaling.2015

SOD in Redox Signaling

Tohru Fukai,etal.Antioxidants&RedoxSignaling.2011

SOD in Redox Signaling

Outline

• Superoxidedismutase(SODs)• Catalases• Peroxiredoxins• Glutathioneperoxidase

2H2O2 ---->O2 +2H2O.

Cofactor:Heme &NADPH

H2O2 +Fe(III)-E→H2O+O=Fe(IV)-E(.+)

H2O2 +O=Fe(IV)-E(.+)→H2O+Fe(III)-E+O2

Catalase

Majorcatalasegenesindifferentspecies

Humans CATgene(EC1.11.1.6)Cytogeneticlocation:11P13

E.coli: katG:encodesbifunctionalcatalase-peroxidaseHPIkatE :encodemonofunctional catalaseHPII(alsorequiresfunctionalkatF gene)katP :foundinthelargeplasmidofenterohaemorrhagic EscherichiacoliO157:H7(similartokatG)

B.subtilis Ingrowingcells:katA (major,expressionlevelscorrelatewithH2O2);katB(notrespondstoH2O2)Spore-specific:katX (enhancesresistanceofgerminatingsporestoH2O2)

S.cerevisiae CTA&CTT

Catalaselocalization

Mainlyinperoxisomeinmammals;

Alsofoundincytosolandmitochondrial.

Catalaseassociateddiseases

Acatalasemia(Takahara disease):Individualsopensores(ulcers)insidethemouththatledtothedeathofsofttissue.

Neurodegenerativedisorders

Outline

• Superoxidedismutase(SODs)• Catalases• Peroxiredoxins• Glutathioneperoxidase

Peroxiredoxins

• Antioxidantenzymesthatreduceanddetoxifyhydrogenperoxide,peroxynitriteandawiderangeoforganichydroperoxides.

• Thiol-specificantioxidantproteins• Controlcytokine-inducedperoxidelevels• Threeclasses:typical2-Cys,atypical2-Cys,and1-Cys

• Localizedprimarilyincytosol– Canalsobefoundwithinmitochondria,chloroplasts,andperoxisomes(associatedwithnucleiandmembranes)

PeroxiredoxinReaction:Step1• Peroxidasereactioncomposedoftwostepsaroundredox-

activecysteine• Step1:consistentacrossallclassesofperoxiredoxins

– Peroxidaticcysteineattackstheperoxidesubstrateandisoxidizedtoacysteinesulfenicacid

Wood,Z.et.al.2003

PeroxiredoxinReaction:Step2• Step2:resolutionofcysteinesulfenicacid

– Differentacrossthethreeclasses• Typical2-CysPeroxiredoxins

– Peroxidaticcysteinesulfenicacidfromonesubunitisattackedbytheresolvingcysteineoftheothersubunit

• Resultsintheformationofanintersubunitdisulfidebonewhichisthenreducedtocompletethecatalyticcycle.

• Atypical2-CysPeroxiredoxins– Samemechanismastypical2-Cys,butare

functionallymonomeric• Boththeperoxidaticcysteineandresolvingcysteine

arecontainedwithinsamepolypeptide

• 1-CysPeroxiredoxins– Conserveonlytheperoxidaticcysteineanddo

notcontainaresolvingcysteine• Cysteinesulfenicacidisreducedbythiol-containing

electrondonors• Thioldonorformstransientmixeddisulfidebondswith

theenzyme,followedbyreductionbyaseconddonorthioltorecycletheenzyme

Wood,Z.et.al.2003

PeroxiredoxinReaction:Step2• Step2:resolutionofcysteinesulfenicacid

– Differentacrossthethreeclasses• Typical2-CysPeroxiredoxins

– Peroxidaticcysteinesulfenicacidfromonesubunitisattackedbytheresolvingcysteineoftheothersubunit

• Resultsintheformationofanintersubunitdisulfidebonewhichisthenreducedtocompletethecatalyticcycle.

• Atypical2-CysPeroxiredoxins– Samemechanismastypical2-Cys,butare

functionallymonomeric• Boththeperoxidaticcysteineandresolvingcysteine

arecontainedwithinsamepolypeptide

• 1-CysPeroxiredoxins– Conserveonlytheperoxidaticcysteineanddo

notcontainaresolvingcysteine• Cysteinesulfenicacidisreducedbythiol-containing

electrondonors• Thioldonorformstransientmixeddisulfidebondswith

theenzyme,followedbyreductionbyaseconddonorthioltorecycletheenzyme

Wood,Z.et.al.2003

PeroxiredoxinReaction:Step2• Step2:resolutionofcysteinesulfenicacid

– Differentacrossthethreeclasses• Typical2-CysPeroxiredoxins

– Peroxidaticcysteinesulfenicacidfromonesubunitisattackedbytheresolvingcysteineoftheothersubunit

• Resultsintheformationofanintersubunitdisulfidebonewhichisthenreducedtocompletethecatalyticcycle.

• Atypical2-CysPeroxiredoxins– Samemechanismastypical2-Cys,butare

functionallymonomeric• Boththeperoxidaticcysteineandresolvingcysteine

arecontainedwithinsamepolypeptide

• 1-CysPeroxiredoxins– Conserveonlytheperoxidaticcysteineanddo

notcontainaresolvingcysteine• Cysteinesulfenicacidisreducedbythiol-containing

electrondonors• Thioldonorformstransientmixeddisulfidebondswith

theenzyme,followedbyreductionbyaseconddonorthioltorecycletheenzyme

Wood,Z.et.al.2003

PeroxiredoxinsinRedoxSignaling:Aging

Detienne,G.et.al.AgingResearchReviews.2018.

Outline

• Superoxidedismutase(SODs)• Catalases• Peroxiredoxins• Glutathioneperoxidase

Biochemicalfunctionsofglutathioneperoxidases(GPXs)

• Protectionagainstoxidativestress

• Reductionoflipidhydroperoxides totheircorrespondingalcohols

• Reductionofhydrogenperoxidetowater

Glutathioneperoxidasereaction

FigurebyErinE.Battin etJuliaL.Brumaghim,2009

ThisreactiondescribesGPXSelenoproteins,butnotGPX5,7,8.

Enzyme GPX1 GPX2 GPX3 GPX4 GPX5 GPX6 GPX7 GPX8

Role DetoxificationofH2O2 andlipidperoxides

Defensebarrieragainstingestedlipidhydroperoxides

DetoxificationofH2O2 andlipidperoxides

Anti-oxidativeandanti-apoptoticactivity

MaintenanceofspermDNAintegrity

_ Stress sensorwhichleadtoGRP78chaperoneactivityincrease

_

Localization cytosolandmitochondria

cytosol Extracellularfluidsincortical peri-tubularspace

Mitochondria,cytosol,nucleus

Secretedproteininepididymis

EmbryosandBowmanglands

ERlumen ER

Jurkovič S.etal.2008;JiaoY.etal.2017

GPXenzymesandlocalization

Thankyou!