title: Cloning, expression and chromosomal localization of a novel human dipeptidyl peptidase (DPP) IV homolog, DPP8.
abstract: Dipeptidyl peptidase (DPP) IV has roles in T-cell costimulation, chemokine biology, type-II diabetes and tumor biology. Fibroblast activation protein (FAP) has been implicated in tumor growth and cirrhosis. Here we describe DPP8, a novel human postproline dipeptidyl aminopeptidase that is homologous to DPPIV and FAP. Northern-blot hybridization showed that the tissue expression of DPP8 mRNA is ubiquitous, similar to that of DPPIV. The DPP8 gene was localized to chromosome 15q22, distinct from a closely related gene at 19p13.3 which we named DPP9. The full-length DPP8 cDNA codes for an 882-amino-acid protein that has about 27% identity and 51% similarity to DPPIV and FAP, but no transmembrane domain and no N-linked or O-linked glycosylation. Western blots and confocal microscopy of transfected COS-7 cells showed DPP8 to be a 100-kDa monomeric protein expressed in the cytoplasm. Purified recombinant DPP8 hydrolyzed the DPPIV substrates Ala-Pro, Arg-Pro and Gly-Pro. Thus recombinant DPP8 shares a postproline dipeptidyl aminopeptidase activity with DPPIV and FAP. DPP8 enzyme activity had a neutral pH optimum consistent with it being nonlysosomal. The similarities between DPP8 and DPPIV in tissue expression pattern and substrates suggests a potential role for DPP8 in T-cell activation and immune function.
authors.affiliation: A. W. Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Centenary Institute of Cancer Medicine and Cell Biologyand The University of Sydney, NSW, Australia. c.abbott@centenary.usyd.edu.au
authors.forename: C A
authors.initials: CA
authors.lastname: Abbott
authors.forename: D M
authors.initials: DM
authors.lastname: Yu
authors.forename: E
authors.initials: E
authors.lastname: Woollatt
authors.forename: G R
authors.initials: GR
authors.lastname: Sutherland
authors.forename: G W
authors.initials: GW
authors.lastname: McCaughan
authors.forename: M D
authors.initials: MD
authors.lastname: Gorrell
mesh_terms: D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D002460:Cell Line; D002874:Chromosome Mapping; D002884:Chromosomes, Human, Pair 15; D002888:Chromosomes, Human, Pair 19; D003001:Cloning, Molecular; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry / Q000235:genetics*; D010450:Endopeptidases; D018093:Gelatinases; D006133:Growth Substances / Q000737:chemistry; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009000:Monocytes / Q000201:enzymology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry; D000099167:Fibroblast Activation Protein Alpha
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D018819:Dipeptidyl Peptidase 4; D010450:Endopeptidases; D018093:Gelatinases; D006133:Growth Substances; D008565:Membrane Proteins; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D000099167:Fibroblast Activation Protein Alpha