AnalysisNote

Proteindeterminedbybiuret.

Application

用于从蛋白质样品中除去DNA。

DNAseIisusedtonickDNAasafirststeptoincorporatelabeledbasesintoDNA.TheenzymefromSigmahasbeenusedduringtheisolationofplasmamembranevesiclesfromNeurosporacrassacellculture.¹IthasalsobeenusedalongwithtrypsinforthepreparationofsinglecellsUSPensionfromrattestes.²

DeoxyribonucleaseIfrombovinepancreashasbeenusedinastudytocompareseveralproceduresforreducingRNasecontaminationinpreparationsofDNase.DeoxyribonucleaseIfrombovinepancreashasalsobeenusedinastudytoinvestigatetheeffectofthecompositionofsodiumdodecylsulfatepreparationsontherenaturationofenzymesafterpolyacrylamidegelelectrophoresis.

PreparationNote

10mg/mLsolutionofDNAseIin0.15MNaClmaylose<10%ofitsactivitywhenstoredforaweekinaliquotsat−20°C.Thesamesolutionsstoredinaliquotsat2-8°Ccanloseapproximately20%activity.Itremainsactiveforuptofivehoursat60°CbetweenpH5and7,andlosesactivityin<10minutesat68°C.Itlosesactivityattherateof6%/hourinacetatebuffer(pH5.0)andtrisbuffer((pH7.2)at1mg/mLconcentration.

DerivedfromNewZealand-sourcedpancreas

UnitDefinition

在pH5.0和25°C下以I型或III型DNA为底物，一个Kunitz单位每分钟产生的ΔA₂₆₀为0.001。[Mg²⁺]=4.2mM。

Physicalform

Crudepreparation,containscalciumchloride

Biochem/physiolActions

DNaseIisanendonucleasethatactsonphosphodiesterbondsadjacenttopyrimidinestoproducepolynucleotideswithterminal5′-phosphates.InthepresenceofMg²⁺,DNAseIcleaveseachstrandofDNAindependentlyandthecleavagesitesarerandom.BothDNAstrandsarecleavedatapproximatelythesamesiteinthepresenceofMn²⁺.³DivalentcationssuchasMn²⁺,Ca²⁺,Co²⁺,andZn²⁺areactivatorsoftheenzyme.Aconcentrationof5mMCa²⁺stABIlizestheenzymeagainstproteolyticdigestion.ThepHoptimumisfoundtobebetween7and8.⁴DNAseIfrombovinepancreasconsistsoffourchromatographicallydistinguishablecomponents,A,B,C,andD,withtheirmolarratiosbeing4:1:1respectively.OnlyminoramountsofDarefound.⁵2-Mercaptoethanol,chelators,sodiumdodecylsulfate(SDS)⁶andactin⁷areknowntoinhibittheenzymeactivity.