Identification of the bile canalicular cell surface molecule GP110 as the ectopeptidase dipeptidyl peptidase IV: an analysis by tissue distribution, purification and N-terminal amino acid sequence.
This paper describes the tissue distribution, purification and N-terminal amino acid sequence of the bile canalicular cell surface molecule dipeptidyl peptidase IV. Immunoperoxidase staining of cryostat sections of rat liver with a monoclonal antibody, Medical Research Council OX-61, indicated specific binding to hepatocyte bile canalicular domains and brush borders of bile ducts. Additional staining was seen in other epithelial brush borders (small intestine, kidney, colon, pancreatic duct); acinar structures in salivary glands; endothelial structures and T cell areas in thymus, spleen and lymph node. The tissue distribution suggested that monoclonal antibody OX-61 binds to the ectoenzyme dipeptidyl peptidase IV. This was confirmed by depletion of dipeptidyl peptidase IV activity from tissue homogenates by monoclonal antibody OX-61 coupled to Sepharose. The molecule recognized by OX-61 was then purified from liver and kidney by monoclonal antibody affinity chromatography. The molecule had a molecular weight of 110 kD under reducing conditions. The purified molecule was subsequently analyzed for amino acid composition and N-terminal amino acid sequence. Thirty-one N-terminal amino acids were sequenced and indicated identity with part of the predicted N-terminus of the previously cloned bile canalicular molecule GP110. On review, other similarities between dipeptidyl peptidase IV and GP110 were detected: molecular weight, deglycosylated form and metabolic half-life. Finally, the recent cloning of dipeptidyl peptidase IV permitted a comparison between the molecule recognized by monoclonal antibody OX-61, GP110 and dipeptidyl peptidase IV. It is concluded that these three molecules are almost certainly identical.
McCaughan
G W
GW
A.W. Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Camperdown NSW, Australia.
Wickson
J E
JE
Creswick
P F
PF
Gorrell
M D
MD
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001648:Bile Canaliculi / Q000201:enzymology*; D001652:Bile Ducts / Q000201:enzymology; D001653:Bile Ducts, Intrahepatic / Q000201:enzymology*; D015153:Blotting, Western; D002846:Chromatography, Affinity; D018819:Dipeptidyl Peptidase 4; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D005110:Extracellular Space / Q000201:enzymology; D007124:Immunoenzyme Techniques; D008099:Liver / Q000201:enzymology; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D051381:Rats; D011917:Rats, Inbred Lew
D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018819:Dipeptidyl Peptidase 4