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Query: UNIPROT:O95477 (membrane-bound)
 29,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proteolytic conversion of oxytocin and vasopressin by purified rat brain synaptic membranes was studied at 37 degrees C and physiological pH 7.4. The formed peptide fragments were isolated by high performance liquid chromatography and characterized by amino acid analysis. When oxytocin was incubated with synaptic membranes, either C- or N-terminal fragments were found. The most abundant were [Cyt6]oxytocin(4-9), [Cyt6]oxytocin(3-9), [Cyt6]oxytocin(2-9), oxytocin(1-8) and oxytocin(1-7). In contrast, only C-terminal fragments, [Cyt6-Arg8]vasopressin(4-9), [Cyt6-Arg8]vasopressin(3-9) and [Cyt6-Arg8]vasopressin(2-9), were found by incubating [Arg8]vasopressin. The formation of C-terminal oxytocin and vasopressin fragments was inhibited by the aminopeptidase inhibitors amastatin and bestatin, while the formation of oxytocin(1-7) and (1-8) was inhibited by the divalent cations Hg(2+) and Zn(2+). The formation of oxytocin(1-7) was also partially prevented by the endopeptidase inhibitor phosphoramidon. The formation of both C- and N-terminal fragments was inhibited by o-phenanthroline. The results suggest that, while [Arg8]vasopressin is metabolized only by membrane-bound aminopeptidases, oxytocin is also metabolized by membrane-bound endopeptidases.
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PMID:Proteolytic conversion of oxytocin by brain synaptic membranes: role of aminopeptidases and endopeptidases. 180 Sep 50

One membrane-bound alpha-glucosidase and two soluble alpha-glucosidases were isolated from homogenates of the hind-midgut, the main digestive region in Musca domestica larvae. The membrane-bound alpha-glucosidase and the low-Mr soluble alpha-glucosidase hydrolyze maltopentaose better than maltose, maltotriose, and maltotetraose, the reverse being true for the high-Mr soluble alpha-glucosidase. A membrane-bound glucoamylase previously described in Musca domestica midgut was shown by gradient centrifugation and dialysis against EDTA to result from the combined action of an amylase and an alpha-glucosidase. The determination of amylase, alpha-glucosidases, soluble and membrane-bound carboxypeptidase A, membrane-bound aminopeptidase and dipeptidase along the tissue and luminal contents of the hind-midgut is described. The data support a proposal concerned with how starch and protein are digested in Musca domestica larval hind-midguts and where and how midgut glycosidases and peptidases are secreted.
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PMID:Regional distribution and substrate specificity of digestive enzymes involved in terminal digestion in Musca domestica hind-midguts. 180 31

The levels of soluble and membrane-bound aminopeptidase activities were assayed in subcellular fractions from young (1 month old) and adult (5 month old) left and right rat brains, using Leu-, Arg- and Asp-2-naphthylamide as substrates. Both soluble Leu- and Arg-aminopeptidase activities showed the highest levels in the synaptosomal fraction in the two groups of rats. The highest levels of membrane-bound Leu- and Arg-aminopeptidase activities were found in the microsomal fraction of the two ages studied. There were no differences between the two ages in soluble Leu- and Arg- aminopeptidase activities. However, a significant decrease in both membrane-bound activities was evidenced in the synaptosomal fraction of adult rats. The young rats showed the highest soluble and membrane-bound levels of Asp-aminopeptidase activity in the microsomal fraction but no differences among fractions were found at 5 months of age. The soluble Asp-aminopeptidase activity of the homogenate and the mitochondrial fraction was significantly increased in adult animals when compared to that of younger ones. Finally, no differences between left and right brains, in soluble or membrane-bound activities, were found neither in young animals nor in the adult ones.
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PMID:[Subcellular distribution of soluble and membrane-bound aminopeptidase in the left and right hemispheres of young and adult rats]. 185 28

The selective distribution of methionyl aminopeptidase (MAP) among rat liver mitochondria (heavy and light) and microsomes is reported. Several properties of MAP from the three subcellular fractions showed that the enzyme is a typical aminopeptidase able to remove N-terminal methionine from oligopeptides and methionyl-2-naphthylamide but not from Met-Ala-Ser. MAP is a membrane-bound enzyme sensitive to SH-group oxidants and inhibitable by L-methionine but not by usual arylaminopeptidase inhibitors. It is suggested that, MAP may play an important role during protein synthesis in rat liver.
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PMID:Methionyl aminopeptidase from rat liver: distribution of the membrane-bound subcellular enzyme. 188 86

We previously found that the myeloid cell surface glycoprotein CD13 (gp150) is identical to aminopeptidase N (EC 3.4.11.2), a widely distributed membrane-bound, zinc-dependent metalloprotease with an extracellular enzymatic domain that cleaves N-terminal amino acid residues from oligopeptides (J Clin Invest 83:1299, 1989). As a first step toward defining the function of this molecule on myeloid cells, we assessed cell surface-associated N-terminal peptidase activity by sensitive spectrophotometric measurements of the cleavage of p-nitroanilide amino acid derivatives. Aminopeptidase activity detected on the surface of normal and malignant hematopoietic cells coincided with the level of cell surface CD13 expression as measured by flow cytometry. The enzyme was specifically inhibited by the zinc-binding metalloprotease inhibitors, bestatin, 1,10-phenanthroline, or 2.2'-dipyridyl, but was not affected by several inhibitors of other classes of proteases. Aminopeptidase activity was demonstrated for CD13 molecules specifically immunoprecipitated from the surface of CD13-positive cells and was blocked by the metalloprotease inhibitor 1,10-phenanthroline. Moreover, cell surface aminopeptidase activity was partially inhibited when viable cells were incubated with two of a panel of 11 monoclonal antibodies (MoAbs) known to be specific for extracellular epitopes of human CD13. This inhibition was apparent in the absence of detectable downmodulation of CD13 molecules from the cell surface, suggesting that these MoAbs either physically interfere with substrate binding or alter the zinc-coordinating properties of aminopeptidase N molecules. Aminopeptidase N could play an important role in modulating signals generated by peptides at the surface of myeloid cells, either by removing key N-terminal residues from active peptides or by converting inactive peptides to active forms. The inhibitory antibodies used in this study should prove useful in delineating the physiologic roles of CD13/aminopeptidase N on normal and malignant myeloid cells.
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PMID:Metalloprotease activity of CD13/aminopeptidase N on the surface of human myeloid cells. 196 20

The alanine aminopeptidase from Acinetobacter calcoaceticus is inhibited by SH-reagents like p-hydroxymercuribenzote, Ellman's reagent, N-bromosuccinimide, and metal chelating agents like 1,10-phenanthroline. The AAP is competitively inhibited by L-amino acids such as leucine, phenylalanine, and valine having hydrophobic side chains. Bacitracin (Ki = 2.0.10(-6) mol/l) inhibits AAP stronger than puromycin (Ki = 8.0.10(-6) mol/l). In contrast, the Aeromonas aminopeptidase (EC 3.4.11.10) is stronger inhibited by bestatin (Ki = 1.8.10(-8) mol/l) than the membrane-bound AAP from Acinetobacter calcoaceticus. However, the binding of bestatin by both membrane-bound enzymes. Acinetobacter-AAP and microsomal aminopeptidase M (EC 3.4.11.2), with Ki values of 8.10(-6) mol/l is in the same range.
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PMID:[A membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus. 3. Inhibition of the enzyme]. 198 Jan 90

The subcellular distribution of soluble and membrane-bound leucyl- and arginyl-aminopeptidase activities were analyzed in one and five month old rat brains using Leu- and Arg-2-naphthylamide as substrates. Both soluble leucyl- and arginyl-aminopeptidase activities showed the highest levels in the synaptosomal fraction in the two groups of rats. The highest levels of membrane-bound leucyl- and arginyl-aminopeptidase activities were found in the microsomal fraction in the two ages studied. There were no differences between the two ages in soluble leucyl- and arginyl-aminopeptidase activities. However, a significant decrease in both membrane-bound enzymatic activities was evidenced in the synaptosomal fraction of older rats. Developmental changes of these aminopeptidase activities in a determined subcellular localization, may reflect modifications in their effect on neuropeptides susceptible to be hydrolyzed in this particular location.
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PMID:Soluble and membrane-bound leucyl- and arginyl-aminopeptidase activities in subcellular fractions of young and adult rat brains. 209 37

The levels of soluble and membrane-bound aminopeptidase activities were assayed in subcellular fractions from young (4 weeks old) and adult (20 weeks old) rat brains, using Asp-2-naphthylamide as substrate. The young rats showed the highest soluble and membrane-bound levels of activity in the microsomal fraction but no differences among fractions were found at 20 weeks of age. The membrane-bound activity was significantly higher than the soluble one in all subcellular fractions of young rats. Soluble activity of the homogenate and the mitochondrial fraction was significantly increased in adult animals when compared to that of younger ones.
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PMID:Mn2(+)-activated aspartate aminopeptidase activity, subcellular localization in young and adult rat brain. 222 12

Enkephalin degradation in brain has been shown to be catalyzed, in part, by a membrane-bound puromycin-sensitive aminopeptidase. A cytosolic puromycin-sensitive aminopeptidase with similar properties also has been described. The relationship between the soluble and membrane forms of the rat brain enzyme is investigated here. Both of these aminopeptidase forms were purified from rat brain and an antiserum was generated to the soluble enzyme. Each of the aminopeptidases is composed of a single polypeptide of molecular mass 100 kilodaltons as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion chromatography. The antisoluble aminopeptidase antiserum reacts with both enzyme forms on immunoblots and inhibits both with nearly identical inhibition curves. The isoelectric points (pI = 5.0) of both forms were shown to be identical. N-terminal sequencing yielded a common sequence (P-E-K-R-P-F-E-R-L-P-T-E-V-S-P-I-N-Y) for both enzyme forms, and peptide mapping yielded 26 peptides that also appeared identical between the two enzyme forms. Studies on the nature of the association of the membrane enzyme form with the cell membrane suggest that this enzyme form does not represent the soluble form trapped during the enzyme preparation. It is suggested that the membrane form of the puromycin-sensitive aminopeptidase is identical to the soluble enzyme and that it associates with the membrane by interactions with other integral membrane proteins.
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PMID:Comparison of the soluble and membrane-bound forms of the puromycin-sensitive enkephalin-degrading aminopeptidases from rat. 229 52

Substance P is a neuropeptide released in vivo from the substantia nigra, the principal substance P nerve terminal region in the rat brain. Its inactivation was investigated in a purified nigral synaptic membrane preparation. The membrane-bound enzyme shares many features with the endopeptidase 24-11 (EC 3.4.24.11): 1) hydrolysis of peptide bonds Gln6-Phe7, Phe7-Phe8 and Gly9-Leu10, 2) sensitivity to the inhibition by phosphoramidon and 3) relative affinity for substance P. Bestatine and captopril inhibit only the hydrolysis of the metabolites. These results suggest that substance P is inactivated in substantia nigra by endopeptidase 24-11 and that a bestatin-sensitive aminopeptidase and angiotensin converting enzyme may play a role in subsequent degradation of the substance P metabolites.
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PMID:Metalloendopeptidase (EC 3.4.24.11) but not angiotensin converting enzyme is involved in the inactivation of substance P by synaptic membranes of the rat substantia nigra. 247 Oct 29


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