摘要
INTRODUCTIONThealternatingaccesstransportermodel(AATM)wasinitiallyconstructedtorationalizeandexplainafewreadilyquantifiableandreproducibleexperimentalfindings.TheAATM,asoriginallyconceived,consistsofsinglespecificbindingsitecentrallysituatedwithinthecellmembrane.Thesitealternatelyfacesinwardsandoutwards.Duringtheinversionprocess,thesitecantransportsugaracrossthemembrane,anddissociationintothealternatebathingsolutionresultsinnettransport.ReturnoftheemptysitereinitiatesthetransportcycleasillustratedinFig.1A.Glucosetransport,whichwasdemonstratedfirstinhumanredcells(LeFevreandLeFevre1952)andsheepplacenta(Widdas1951),hashighstereospecificityforD-pyranosesugars,likeD-glucoseandD-xyloseinpreferencetoL-sugars,e.g.L-fructoseornon-transportedL-glucose.Thistransportprocesshassimilaritiestoenzymekinetics:bothhavesaturationkinetics,theKmbeingtheconcentrationatwhichhalfmaximaltransportvelocity,Vmaxobtained,isameasureofapparentaffinityofligandforthetransporter(Fig.1B).Theprocessispassiveinthehumanredcell,sinceatequilibriumtheglucoseconcentrationsintheextraandintracellularsolutionsarethesame;i.e.netuphillaccumulationdoesnotoccur.
出版日期
2018年06月16日（中国期刊网平台首次上网日期，不代表论文的发表时间）
