CLONING AND CHARACTERIZATION OF A NOVEL PEPTIDASE FROM RAT AND HUMAN ILEUM

A novel 100-kDa ileal brush border membrane protein (I100) has been pu rified by anionic glycocholate affinity chromatography, Polyclonal ant ibodies raised against this protein were utilized to clone and charact erize I100 in rats, A partial length human I100 cDNA was identified by hybridization screening, In the rat, the I100 protein is a 746-amino acid glycosylated (calculated core molecular mass of 80 kDa) type II i ntegral membrane protein found on the apical surface of ileal villus e nterocytes, Its a,6-kilobase mRNA is expressed in distal small intesti ne in rats and in humans, The I100 cDNA is homologous to but distinct from human prostate-specific membrane antigen and rat brain N-acetylas partylglutamate peptidase, It is expressed on both the basolateral and apical surfaces of stably transfected Madin Darby canine kidney cells , Analysis of these stably transfected Madin Darby canine kidney cells and I100 immunoprecipitates of rat ileal brush border membrane vesicl es reveals that it has dipeptidyl peptidase TV activity. Future invesi tgations will need to determine the exact substrate specificity of thi s novel peptidase.