I.U.B.:3.4.23.1

Pepsinisanacidicprotease.Itsinactivezymogenprecursor,pepsinogen,isproducedinthestomachmucosa.ThereareseveralpepsinsdesignatedA,B,C,andD.PepsinA,themajorcomponent,hasamolecularweightof35,000daltonsandanoptimumpHofapproximately1.0forsubstratessuchascaseinorhemoglobinifthesubstrateisnativeprotein.Pepsincleavesproteinspreferentiallyatcarboxylicgroupsofaromaticaminoacidssuchasphenylalanineandtyrosine.Itwillnotcleaveatbondscontainingvaline,alanineorglycine.PepsinisassayedbasedonthemethodofAnsonJ.Gen.Physiol.,22,79(1938)usinghemoglobinasthesubstrate.PepsinisunstableabovepH6.

StABIlity/Storage:Pepsinfor1-2yearsat2-8°C.

UnitDefinition:OneUnitreleases0.001A280asTCAsolublehydrolysisproductsfromdenaturedhemoglobinperminuteat37°C.OneFIPUnit,expressedasmicromolesoftyrosineequivalentsliberatedperminuteat25°C,canbecalculatedasfollows:1WorthingtonUnitx0.0071=FIPunits.

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