Identification of a membrane-bound carboxypeptidase as the mammalian homolog of duck gp180, a hepatitis B virus-binding protein.
A unique membrane-bound carboxypeptidase was discovered and characterized in membrane fractions of human skin fibroblasts and the mouse monocyte-macrophage cell line J774A.1 and was partially purified from human placenta. Enzymatic characterization identified it as a new member of the regulatory B-type metallocarboxypeptidases, different from carboxypeptidases B, E, M, N and U. It is, however, similar to the newly described bovine carboxypeptidase D, suggested to be a homolog of duck gp180, a 180 kDa hepatitis B virus-binding protein. To prove this, a partial cDNA encoding a 20 kDa fragment of the human homolog of duck gp180 was expressed in bacteria and the recombinant protein was purified. Antibodies raised to the protein immunoprecipitated 94% or 72% of the low pH carboxypeptidase activity in human skin fibroblasts or J774A.1 cells and gave a 175 kDa protein band in Western blots. Thus, carboxypeptidase D is the mammalian homolog of duck gp180 and is distributed in a variety of different cell types.
McGwire
G B
GB
Department of Pharmacology, University of Illinois College of Medicine, Chicago 60612, USA.
Tan
F
F
Michel
B
B
Rehli
M
M
Skidgel
R A
RA
D000818:Animals; D015152:Blotting, Northern; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology*; D003035:Cobalt / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006515:Hepatitis B virus / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D010920:Placenta / Q000201:enzymology; D011233:Precipitin Tests; D011506:Proteins; D011994:Recombinant Proteins / Q000378:metabolism
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D011506:Proteins; D011994:Recombinant Proteins; D003035:Cobalt; D002268:Carboxypeptidases; C094315:metallocarboxypeptidase D