Biosynthesis and intracellular pool of aminopeptidase N in rabbit enterocytes.
A papain treatment at 15 degrees C and pH 7.3 of a microsomal fraction from rabbit enterocytes quantitatively releases the aminopeptidase N integrated in the plasma membranes without solubilizing the enzyme integrated in the intracellular membranes. Working on A+ rabbits, characterized by the presence on the brush-border hydrolases of glycans corresponding to the human blood group A-determinant structure, it was possible to separate the intracellular aminopeptidase into two major molecular forms with or without these determinants. The molecular form devoid of human blood group A antigenicity corresponds to the only stable intermediate of glycosylation, bearing N-linked high mannose oligosaccharides. This endoglycosidase H-sensitive form is fully active and represents in the steady state about 1% of the total cellular aminopeptidase. It contains a cytoplasmic sequence of about 3000 daltons that has not yet been detected in the mature form. The A antigenicity is acquired simultaneously with processing of high mannose glycans to complex glycans. Pulse chase labeling of jejunum loops with [35S]-methionine showed that the complete processing of the transient form synthesized during 10 min takes 1 hr. During the last 30 min of processing, all the newly transformed molecules are transported to the plasma membrane.
Feracci
H
H
Rigal
A
A
Maroux
S
S
D000626:Aminopeptidases / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D018826:CD13 Antigens; D002462:Cell Membrane / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D007413:Intestinal Mucosa / Q000166:cytology / Q000201:enzymology*; D007583:Jejunum / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D008871:Microvilli / Q000201:enzymology; D010206:Papain; D010446:Peptide Fragments / Q000032:analysis; D011817:Rabbits
D010446:Peptide Fragments; D000626:Aminopeptidases; D018826:CD13 Antigens; D010206:Papain