Post-translational control of de novo cell wall formation during Blastocladiella emersonii zoospore germination: Feedback regulation of hexosamine biosynthesis☆

[摘要] TheBlastocladiellaemersoniizoosporedoesnotcontainsufficienttotalhexosaminetoaccountforthechitincontentofthecellwallformedduringgermination.Itisnotdeficientintheenzymesneededtosynthesizechitinfromfructose-6-phosphateandglutamine.Theenzymesofhexosaminebiosynthesisarelocateddifferentlyinthezoosporethanchitinsynthetase.Uridine-5′-diphospho-N-acetylglucosamine(UDPGlcNAc),theendproductofhexosaminesynthesisandasubstrateforchitinsynthesis,reversiblyinhibitstheactivityofonlythefirstpathway-specificenzymeatconcentrationsbelowthatestimatedtoexistinthezoospore.UDPGlcNAccombineswiththeenzyme-glutaminecomplexindirectcompetitionwithfructose-6-phosphate.Uridinenucleosidephosphates,producedthroughtheutilizationofUDPGlcNAcinchitinsynthesis,directlycompetewiththeinhibitoryeffectsofUDPGlcNAc,whileothernucleosidephosphatescanenhancetheinhibitionduetoUDPGlcNAc.ThedataareconsistentwiththesimultaneousbindingofUDPGlcNAcattwoenzymesitestoinhibitcatalysis—thesubstrate(fructose-6-phosphate)siteandtheuridinenucleosidephosphatesite.Thehexosaminepathwaycanbenegativelyregulated,asitisinthezoospore,byUDPGlcNAcandcanbepositivelyregulated,asitisduringzoosporegermination,byloweringUDPGlcNAcconcentrationandraisingUDP+UTPconcentrations.OthervariationsinthesemetabolitescouldregulatehexosaminebiosynthesisduringotherphasesoftheB.emersoniilifecycle.

[学科分类] 生物科学（综合）