Formulation	50%glycerol/water(v/v)
Storage	-20°C
Purity	>95%bySDS-PAGE
ActivityDetermination	FactorXIclottingassay
ShelfLife(properlystored)	12months

ProteolyticActivationofFactorXI
TheactivationoffactorXIbyfactorXIIaisillustrated.AlthoughfactorXIcanbindindependentlytonegativelychargedsurfaces,proteolysisbyfactorXIIacanonlyoccurinthepresenceofsurface-boundhighmolecularweightkininogen(HMWKa).TheboundHMWKaissusceptIBLetoproteolysisbythenewlygeneratedfactorXIawhichresultsinalossofitsBIOLOGicalactivity(HMWKi).FactorXIacatalyzestheproteolyticconversionoffactorIXtofactorIXaeitherinsolutionphaseorwhenboundtoanegativelychargedsurface.

SampleGelInformation:

Gel	Novex4-12%Bis-Tris
Load	HumanFactorXIa,1µgperlane
Buffer	MOPS
Standard	SeeBluePlus2;Myosin(191kDa),PhosphorylaseB(97kDa),BSA(64kDa),GlutamicDehydrogenase(51kDa),AlcoholDehydrogenase(39kDa),CarbonicAnhydrase(28kDa),MyoglobinRed(19kDa),Lysozyme(14kDa)

Overview:

ProteolysisofXIbyfactorXIIainthepresenceofhighmolecularweightkininogen(HMWK),yieldstheenzymefactorXIa(1-3).FactorXIaisaserineproteasewhichparticipatesintheintrinsicpathwayofcoagulationbycatalyzingtheconversionoffactorIXtofactorIXa.BecausefactorXIisahomodimer,theenzyme,factorXIa,iscomposedoftwoidenticalheavychains(Mr=50,000),andtwoidenticallightchains(Mr=30,000),allofwhichareheldtogetherbydisulfidebonds.ThislatterpropertymakesfactorXIauniqueamongtheserineproteases,sinceitcontainstwoactivesitespermolecule(1-3).

FactorXIa,likeitsprecursorfactorXI,remainsincomplexwithHMWK(4).Incomplexform,factorXIa/HMWKiscapableofactivatingfactorXIItofactorXIIaandprekallikreintokallikrein.Additionally,inthecomplexedform,factorXIaislessaffectedbyproteaseinhibitors(5).ThemajorplasmainhibitoroffactorXIaisa1-antitrypsinandthentoamuchlesserextent,antithrombin-III(5,6).Whileinthecomplexedform,factorXIamaycatalyzetheproteolysisofHMWK,yieldingabiologicallyinactiveformofHMWK(HMWKi),thusallowingdissociationoftheFactorXIa/HMWKicomplex.EitherfreefactorXIaorthefactorXIa/HMWKcomplexcatalyzestheproteolyticconversionoffactorIXtofactorIXa.

FactorXIaispreparedbyactivatingpurifiedfactorXIwithfactorXIIa.Followingactivation,themixtureispassedoveracolumnofimmobilizedanti-factorXIItoremovethefactorXIIa,andfurtherpurifiedonheparin-Sepharose.ThefactorXIaissuppliedin50%(vol/vol)glycerol/H2Oandshouldbestoredat-20°C.PurityisassessedbySDSPAGEanalysis.ActivityisdeterminedinaclottingassayusingfactorXIdeficientplasma.

Properties:

Localization	Plasma;inassociationwithhighmolecularweightkininogen
Modeofaction	AserineproteasethatconvertsfactorIXtofactorIXa
Molecularweight	160,000(1,2)
Extinctioncoefficient	E 1% 1cm,280nm =13.4(human)(2)-(inferredfromthezymogen,factorXI)
Structure	twoapparentlyidenticalheavychains(Mr~50,000)andtwoapparentlyidenticallightchains(Mr~30,000)heldtogetherbydisulfidebonds.Eachlightchaincontainsacatalyticdomain(1,3).
Percentcarbohydrate	5%(human)(1)

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