MEMBRANE AMINE OXIDASE CLONING AND IDENTIFICATION AS A MAJOR PROTEIN IN THE ADIPOCYTE PLASMA-MEMBRANE

A 97-kDa protein present in the glucose transporter (GLUT4 isotype)-co ntaining vesicles from rat adipocytes has been isolated, the sequences of two tryptic peptides were obtained, and on the basis of these its cDNA partially cloned, The 97-kDa protein is almost certainly identica l to a major integral glycoprotein of this size in the rat adipocyte p lasma membrane, since its predicted N-terminal sequence is the same as that recently determined for this glycoprotein by amino acid sequenci ng, Moreover, the predicted partial sequence (322 amino acids) of the 97-kDa protein is highly homologous to the corresponding region of a h uman placental amine oxidase, which was cloned simultaneously and prop osed to be a secreted protein. The amino acid sequence of the 97-kDa r at/human amine oxidase indicates that the protein consists of a very s hort N-terminal cytoplasmic domain followed by a single transmembrane segment and a large extracellular domain containing the catalytic site , Thus this study establishes the 97-kDa rat/human amine oxidase as th e first integral membrane amine oxidase to be cloned, The membrane ami ne oxidase was more abundant in the plasma membranes than the low dens ity microsomes of the adipocyte, and in contrast to some other protein s found in GLUT4 vesicles, it did not redistribute to the plasma membr ane in response to treatment of the cells with insulin.