BackgroundInformation | Gutamicaciddecarboxylase(GAD;E.C.4.1.1.15)istheenzymeresponsIBLefortheconversionofglutamicacidtogamma-aminobutyricacid(GABA),themajorinhibitorytransmitterinhigherbrainregions,andputativeparacrinehormoneinpancreaticislets.TwomolecularformsofGAD(65kDaand67kDa,64%aaidentitybetweenforms)arehighlyconservedandbothformsareexpressedintheCNS,pancreaticisletcells,testis,oviductandovary.Theisoformsareregionallydistributedcytoplasmicallyinthebrainsofratsandmice(Sheikh,S.etal.1999).GAD65isanampiphilic,membrane-anchoredprotein(585a.a.),encodedonhumanchromosome10,andisresponsibleforvesicularGABAproduction.GAD67iscytoplasmic(594a.a.),encodedonchromosome2,andseemstoberesponsibleforsignificantcytoplasmicGABAproduction.GADexpressionchangesduringneuraldevelopmentinratspinalcord.ColocalizationofthetwoGADisoformsalsoshowschangesinGAD65/GAD67distributionscorrelatedwithcertaindiseasestatessuchasIDDMandSMS. |