Biosynthesis of intestinal microvillar proteins. Dimerization of aminopeptidase N and lactase-phlorizin hydrolase

• Published in: Biochemistry (Easton) Vol. 29; no. 1; pp. 305 - 308
• Main Author: Danielsen, E. Michael
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 09.01.1990
• Subjects: AMINO ACIDS; AMINOPEPTIDASES; Aminopeptidases - biosynthesis; Analytical, structural and metabolic biochemistry; ANIMALS; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; beta-Galactosidase - biosynthesis; BETA-MINUS DECAY RADIOISOTOPES; Biological and medical sciences; BIOSYNTHESIS; BODY; CARBOXYLIC ACIDS; CD13 Antigens; CELL CONSTITUENTS; CHEMICAL REACTIONS; CROSS-LINKING; DAYS LIVING RADIOISOTOPES; DIGESTIVE SYSTEM; DIMERIZATION; Dimethyl Adipimidate - metabolism; DOMESTIC ANIMALS; DRUGS; ELECTROPHORESIS; ENZYMES; Enzymes and enzyme inhibitors; EVEN-ODD NUCLEI; Fundamental and applied biological sciences. Psychology; Galactosidases - biosynthesis; GASTROINTESTINAL TRACT; Glucosidases - biosynthesis; GLYCOPROTEINS; GLYCOSYL HYDROLASES; HYDROLASES; Intestinal Mucosa - enzymology; Intestinal Mucosa - ultrastructure; INTESTINES; ISOTOPES; Kinetics; Lactase-Phlorizin Hydrolase - biosynthesis; LIGHT NUCLEI; LIPOTROPIC FACTORS; MAMMALS; MEMBRANES; METHIONINE; Microvilli - enzymology; MUCOUS MEMBRANES; NUCLEI; O-GLYCOSYL HYDROLASES; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC SULFUR COMPOUNDS; ORGANS; PEPTIDE HYDROLASES; POLYMERIZATION; Protein Processing, Post-Translational; PROTEINS; RADIOISOTOPES; SULFUR 35; SULFUR ISOTOPES; SWINE; SYNTHESIS; VERTEBRATES 550201 > Biochemistry > Tracer Techniques; Radiolabelling; Gel electrophoresis; Enzyme; Mucosa; Gut; Explant; Biosynthesis; Pig; Vertebrata; Brush border; Mammalia; Artiodactyla; Kinetics; Densitometry; Aminopeptidase; Immunoelectrophoresis; Localization; Dimerization; Ungulata
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00453a042

The pig intestinal brush border enzymes aminopeptidase N (EC 3.4.11.2) and lactase-phlorizin hydrolase (EC 3.2.1.23-62) are present in the microvillar membrane as homodimers. Dimethyl adipimidate was used to cross-link the two [35S]methionine-labeled brush border enzymes from cultured mucosal explants. For aminopeptidase N, dimerization did not begin until 5-10 min after synthesis, and maximal dimerization by cross-linking of the transient form of the enzyme required 1 h, whereas the mature form of aminopeptidase N cross-linked with unchanged efficiency from 45 min to 3 h of labeling. Formation of dimers of this enzyme therefore occurs prior to the Golgi-associated processing, and the slow rate of dimerization may be the rate-limiting step in the transport from the endoplasmic reticulum to the Golgi complex. For lactase-phlorizin hydrolase, the posttranslational processing includes a proteolytic cleavage of its high molecular weight precursor. Since only the mature form and not the precursor of this enzyme could be cross-linked, formation of tightly associated dimers only takes place after transport out of the endoplasmic reticulum. Dimerization of the two brush border enzymes therefore seems to occur in different organelles of the enterocyte.