Release of glucose-6-phosphate dehydrogenase from cortex of Spisula eggs at fertilization and its recombination after meiosis☆

[摘要] Changesinsubcellulardistributionsofglucose-6-phosphatedehydrogenase(G6PDH)wereobservedafterfertilizationorartificial(KCl)activationofSpisulaeggs.ThoughthetotalactivityofG6PDHdidnotchangeduringearlystages,thatinthe100,000gsupernatantfractionincreasedafterfertilization,attainedamaximumatthefirstmeioticmetaphase,andthendecreased.Thischangeofactivityinthesupernatantwasaccompaniedbyamirror-imagechangeofactivityinthepellet.MostoftheG6PDHwaslocalizedinthe3000gpelletfraction;furthermore,theactivityinisolatedcorticesshowedfluctuationsduringmeiosissimilartothatofthe3000gpelletfraction.ConditionsforthereleaseandbindingoftheNADP-specificG6PDHfromthepelletfractionwereinvestigatedinvitro.NADP+orNADPHcaninducereleaseofG6PDH,althoughNADPHisthreetofourtimesmoreefficientthanNADP+.NAD+doesnotaffectrelease.Highconcentrationsofsalts(ionicstrength>0.3)causedcompleteG6PDHreleasefromthepellet.AlthoughraisingthepHaloneshowedonlyaslightreleasingeffect,increaseofpHtopH7oraboveconsiderablyaugmentedreleaseduetoNADP+orNADPH.ThereleaseofG6PDHfromthepelletfractionwasshowntobereversible.TheseresultssuggestthatthereversibleassociationofG6PDHwithparticulatecomponentsofthecytoplasmmayplayanimportantroleinregulationofG6PDHactivityinmarineeggsandthatthecortexisoneofthesiteswhichmaybeinvolvedinsuchregulation.ThemechanismofrecombinationofG6PDHwithitssitesremainstobeelucidated.

[学科分类] 生物科学（综合）