Distribution and biosynthesis of aminopeptidase n and dipeptidyl aminopeptidase IV in rat small intestine

• Published in: Biochimica et biophysica acta Vol. 761; no. 1; pp. 66 - 75
• Main Authors: Miura, Soichiro, Song, In-Sung, Morita, Akira, Erickson, Roger H., Kim, Young S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22.11.1983; Elsevier; North-Holland
• Subjects: Aminopeptidase N; Aminopeptidases - isolation & purification; Aminopeptidases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; CD13 Antigens; Cytosol - enzymology; Dipeptidyl aminopeptidase IV; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases - isolation & purification; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases - metabolism; Endopeptidases - metabolism; Enzyme distribuin; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Golgi Apparatus - enzymology; Hydrolases; Intestinal Mucosa - enzymology; Intestine, Small - enzymology; Male; Microvilli - enzymology; Radioimmunoassay; Rat small intestine; Rats; Rats, Inbred Strains; Dipeptidyl aminopeptidase IV; Rat small intestine; Radioimmunoassay; Aminopeptidase N; Enzyme distribuin; Peptidase; Rat; Enzyme; Rodentia; Biosynthesis; Small intestine; Golgi apparatus; Vertebrata; Brush border; Mammalia; Aminopeptidase (microsomal); Dipeptidyl peptidase I; Localization; Dipeptidyl peptidase II
• DOI: 10.1016/0304-4165(83)90363-X
• ISSN: 0304-4165; 0006-3002

The regional, cellular and subcellular distribution patterns of aminopeptidase N d dipeptidyl aminopeptidase IV were examined in rat small intestine. Aminopeptidyl N of brush border mebrane had maximal activity in the upper and middle intestine, while dipeptidyl aminopeptidaseV had a more uniform distribution profile with relatively high in the ileum. Along the villus and crypt cell gradient, the activity of both enzymes was maximally expressed in the mid-villus cells. However there was substantial dipeptidyl aminopeptidase IV activity in the crypt cell. Both enzymes were primarily associated with brush border membranesin all segments, however, in the proximal intestine, a significant amount of dipeptidyl aminopeptidase IV activity was associated with the cytosol fraction. The cytosol and brush border membrane forms of dipeptidyl aminopeptidase IV were immunologically identical and had the same electrophoretic mobility on disc gels. In contrast, the soluble and brush border membrane-bound forms of aminopeptidase N were immunologically distinct. When the total amount of aminopeptidase N and dipeptidyl aminopeptidase IV was determined by competitive radioimmunoassay, there were no regional or cellular differences in specific activity (enzyme activity / mg of enzyme protein) of either enzyme in brush border membrane and homogenate. The specific activity of both enzymes in a purified Golgi membrane fraction as measured by radioimmunoassay was about half that of the brush border membrane fraction. These results suggest that (1) aminopeptidase N and dipeptidyl aminopeptidase IV have different regional, cellular and subcellular distribution patterns; (2) there are enzymatically inactive forms of both enzymes present in a constant proportion to active molecules and that (3) a two-fol activation of precursor enzyme forms occurs during transfer from the Golgi membraanes to the brush border membranes.