SEARCH · PubMed Health

Results for “AMINOPEPTIDASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources

PubMed1992

The monoclonal antibody ER-BMDM1 recognizes a macrophage and dendritic cell differentiation antigen with aminopeptidase activity.

Here we describe the reactivity of monoclonal antibody (mAb) ER-BMDM1, directed against a 160-kDa cell membrane-associated antigen (Ag) with amino-peptidase activity. The aminopeptidase recognized by ER-BMDM1 is present on various mouse macrophage (M phi) and dendritic cell (DC) subpopulations as well as on microvillous epithelia. Analysis of ER-BMDM1 Ag expression in in vitro models of M phi maturation revealed that the Ag is expressed at increasing levels upon maturation of M phi. In vivo, high level expression of the ER-BMDM1 Ag occurs after the monocytic stage of maturation, since bone marrow cells and peripheral blood monocytes are essentially ER-BMDM1 negative. Analysis of isolated-resident and elicited M phi populations showed that ER-BMDM1 recognizes a specific subpopulation of mature M phi: only some resident peritoneal and alveolar M phi are ER-BMDM1 positive, whereas virtually all thioglycollate-elicited peritoneal exudate M phi bind the mAb. In lymphoid organs, a subpopulation of M phi is recognized as well as interdigitating cells (IDC) located in T cell areas. Phenotypic analysis of isolated DC--the in vitro equivalents of IDC--from spleen and lymph nodes confirmed that the majority of this important antigen-presenting cell population expresses the ER-BMDM1 aminopeptidase. The molecular characteristics of the ER-BMDM1 Ag suggest that it may represent the mouse homolog of human CD13.

Aminopeptidases↗

PubMed2002

Puromycin insensitive leucyl-specific aminopeptidase (PILSAP) is involved in the activation of endothelial integrins.

We previously reported that mouse orthologue of puromycin insensitive leucyl-specific aminopeptidase (mPILSAP) played an important role in angiogenesis by regulating the proliferation and migration of endothelial cells (ECs) (Miyashita et al., 2002. Blood 99:3241-3249). Here, we examined the mechanism as to how mPILSAP regulates the migration of ECs. Cell adhesion through integrins plays a crucial role in cell migration, and ECs use at least type-1 collagen receptor integrin alpha2beta1, fibronectin receptor alpha5beta1, and vitronectin receptors alphavbeta3 and alphavbeta5. mPILSAP antisense oligodeoxynucleotide (AS-ODN) or leucinethiol (LT), a leucyl-aminopeptidase inhibitor, did not affect the attachment but did significantly inhibit the spreading of cells of the murine endothelial cell line MSS31 when they were plated on vitronectin-, fibronectin-, or type-1 collagen, although they did not affect the expression of integrin alpha2, alpha5, alphav, beta1, beta3, and beta5 subunits on the cell surface. AS-ODN and LT also inhibited the tyrosine phosphorylation of FAK when cells were plated on vitronectin, fibronectin, or type-1 collagen. This inhibition of cell spreading and of tyrosine phosphorylation of FAK could be negated by Mg(2+). These results suggest that mPILSAP is involved in the activation of endothelial integrins.

Androstadienes↗

PubMed2003

Aminopeptidases function as endocytic receptors in the trophotaenial placenta of the goodeid fish, Ameca splendens (Teleostei: Atheriniformes).

Viviparity in goodeid teleosts is characterized by the elaboration of trophotaeniae, extraembryonic proctodaeal appendages facilitating maternal-embryonic nutrient transfer. The trophotaenial absorptive cells (TACs) express aminopeptidases (APs) such as APA, APN, gamma-glutamyltransferase (gamma-GT), dipeptidyl aminopeptidase (DAP) IV, and neutral endopeptidase (NEP) as inferred from the results of cleavage experiments with, respectively, Glu-alpha-(4M beta NA), Ala-(4M beta NA), Glu-gamma-(4M beta NA), Gly-Pro-(4M beta NA), and Gl-(Ala)(3)-(4M beta NA). Enzyme reaction product was localized to the apical and basolateral plasma membrane as well as to some intracellular compartments. In the accompanying report (Schindler, 2003) evidence is presented that the trophotaeniae of Ameca splendens embryos randomly, yet specifically, bind and ingest proteins as well as certain copolymers of amino acids. Present results demonstrate that endocytosis is significantly inhibitable by unspecific proteinase inhibitors, such as diisopropylphosphorofluoride, phenylmethanesulfonylfluoride, antipain, 1.10-phenanthroline, and dithiothreitol. The specific microbial AP inhibitors amastatin, bestatin, and phosphoramidon suppressed protein binding to TACs more effectively when added in combination than did either agent alone. Moreover, in the presence of 4M beta NA assay substrates of APs the capability of TACs to bind proteins was significantly reduced. Conversely, the rate at which 4M beta NA substrates were cleaved by trophotaenial APs was modified in the presence of proteins. Depending on protein concentrations the AP-catalyzed reactions either decreased or increased in velocity. Analysis of the enzyme kinetics by methods of linear transformation suggests that proteins bind to APs competitively, thereby adopting the role of enzyme inhibitors. On the other hand, protein binding to APs appears to be a signal to translocate enzymes from an internal pool to the surface membrane. In the presence of primaquine, the rate of AP-catalyzed cleavage of 4M beta NA substrates was significantly reduced. That can be put down to the fact that weak bases disrupt the recycling of endocytosed membrane constituents. In conclusion, there is evidence that APs in the trophotaenial placenta of A. splendens function as scavenger receptors mediating in the delivery of embryotrophic proteins for lysosomal degradation.

Aminopeptidases↗

PubMed1985

FACS quantitation of leucine aminopeptidase and acid phosphatase on tumor-associated macrophages from metastatic and nonmetastatic mouse mammary tumors.

Macrophages were isolated by adherence from tumors produced by a number of murine mammary carcinoma lines and were examined by fluorescence-activated cell sorting for quantitation of leucine aminopeptidase and acid phosphatase. The tumors included three lines, 66, 67, and 168, which were originally derived from a single, spontaneously arising tumor in a BALB/cfC3H mouse and two other lines, D2A1 and D2F2, which were derived from a single tumor arising from the transplantable hyperplastic alveolar nodule line, D2. These five lines differ from one another in a number of characteristics, including the ability to metastasize spontaneously to the lung from subcutaneous implants and to form experimental metastases in lungs following intravenous injection. Line 67 is nonmetastatic under both circumstances, whereas lines 66, D2A1, and D2F2 are metastatic under the same conditions. Intermediate to these is line 168, which is nonmetastatic from the subcutaneous site but capable of colonizing the lung with an efficiency similar to 66 when injected IV. Tumor-associated macrophages (TAM) from lines 66, D2A1, and D2F2 contained the greatest amounts of leucine aminopeptidase (LAP) and those from line 67 the least, with TAM from 168 being intermediate. Conversely, the TAM from line 67 had the greatest amounts of acid phosphatase (APTase) and those from line 168 the least. In addition to differences among tumors in enzyme levels of the adherent TAM, the precentages of TAM that were adherent were also different among the tumors. Only 12% of TAM from line 67 were recovered in the adherent fraction as opposed to 35-38% of TAM from lines 66 and 168. These results confirm and extend our previous findings that TAM from metastatic tumors have increased levels of LAP compared to TAM from nonmetastatic tumors. They also demonstrate noncoordinate expression of LAP and APTase in TAM, and illustrate how a population of TAM can be homogeneous for one enzyme and heterogeneous for another. Furthermore, the difference in the percentage of macrophages that are adherent between metastatic and nonmetastatic tumors is another indication both of the heterogeneous nature of TAM and of the role of a tumor in determining the type of host infiltrate with which it is associated.

Acid Phosphatase↗

PubMed1988

Major rat brain membrane-associated and cytosolic enkephalin-degrading aminopeptidases: comparison studies.

The major cytosolic and membrane-associated enkephalin-degrading aminopeptidases were purified in parallel by column chromatography successively on DEAE-cellulose, AH-Sepharose, hydroxylapatite, Sephadex G-200, Affigel Blue, AH-Sepharose, and hydroxylapatite. With the final hydroxylapatite column, the cytosol (S) and the membrane (M) enzymes could each be resolved into two peaks, one eluted with 0.05 M phosphate (SI, MI) and the other with 0.25 M phosphate (SII, MII). The overall purification, with Arg BNA as substrate, for the SI and MI was about 450-fold; for SII and MII, 1,200-fold. The yield for each enzyme was about 2%. the major protein integral units of the four enzymes are similar; they are single polypeptide chains with a molecular weight of 100,000 daltons. Their pH optimum, substrate specificity, and sensitivity to puromycin show that they are similar to lysosomal aminopeptidase (EC 3.4.11.-). The two forms of the cytosol and the membrane enzymes have slightly different kinetic constants. With the inhibitors, SII is more sensitive to proctolin, whereas MII is more sensitive to bestatin and Arg-Phe-Ala. Mn2+ activates SI on Met-enkephalin degradation, but inhibits SII, MI, and MII.

Aminopeptidases↗

PubMed1989

Prodrugs of peptides. IV: Bioreversible derivatization of the pyroglutamyl group by N-acylation and N-aminomethylation to effect protection against pyroglutamyl aminopeptidase.

Various N-acyl derivatives and N-Mannich bases of the model compound L-pyroglutamyl benzylamide were synthesized to assess their suitability as prodrug forms for the N-terminal pyroglutamyl residue occurring in several peptides, with the aim of improving peptide delivery characteristics. Whereas pyroglutamyl benzylamide was rapidly hydrolyzed by pyroglutamyl aminopeptidase, the N-acyl derivatives and N-Mannich bases (N-aminomethyl derivatives) were totally resistant to cleavage by the enzyme. On the other hand, these derivatives are readily bioreversible, the conversion to the parent pyroglutamyl amide taking place either by spontaneous hydrolysis at physiological pH, as demonstrated for the N-Mannich bases, or by plasma enzymes, as shown for the N-acyl derivatives. The results suggest that by appropriate N-acylation or N-aminomethylation it may be feasible to protect pyroglutamyl-containing peptides against cleavage by pyroglutamyl aminopeptidase and to obtain a release of the parent peptide in the organism, hence improving the delivery characteristics of such peptides.

Acylation↗

PubMed2006

Cyclic insulin-regulated aminopeptidase (IRAP)/AT4 receptor ligands.

The angiotensin IV receptor (AT4 receptor) is the insulin-regulated aminopeptidase enzyme (IRAP, EC 3.4.11.3). This membrane-spanning enzyme belongs to the M1 family of zinc-dependent metallo-peptidases. It has been proposed that AT4 receptor ligands exert their physiological effects by binding to the active site of IRAP and thereby inhibiting the catalytic activity of the enzyme. The biological activity of a large series of linear angiotensin IV analogs was previously disclosed. Herein, the synthesis and biological evaluation of a series of angiotensin IV analogs, encompassing macrocyclic ring systems of different sizes, are presented. It is demonstrated that disulfide cyclizations of angiotensin IV can deliver ligands with high IRAP/AT4 receptor affinity. One ligand, with an 11-membered ring system (4), inhibited human IRAP and aminopeptidase N (AP-N) activity with similar potency as angiotensin IV but was considerably more stable than angiotensin IV toward enzymatic degradation. The compound provides a promising starting point for further optimization toward more drug-like derivatives. The cyclic constrained analogs allowed us to propose a tentative bioactive conformation of angiotensin IV and it seems that the peptide adopts an inverse gamma-turn at the C-terminal.

Angiotensin II↗

PubMed1993

Purification and characterization of aminopeptidase yspI from Schizosaccharomyces pombe.

Aminopeptidase yspI was purified to apparent homogeneity from the fission yeast Schizosaccharomyces pombe. The molecular mass of the native enzyme was estimated to be 184 kDa by gel filtration chromatography. A value of 92 kDa was calculated after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is thus a dimer with two identical subunits. Optimum pH for cleavage of synthetic aminoacyl-4-nitroanilides is 7.0. Mercury ions, EDTA and chloroquine were found to be potent inhibitors of aminopeptidase yspI activity. Substrate specificity studies indicate that the purified enzyme cleaves L-lysine-4-nitroanilide with high efficiency.

Amino Acid Sequence↗

PubMed1994

Guinea pig membrane-bound aminopeptidase P is a member of the proline peptidase family.

Members of the newly recognized proline peptidase family share the ability to hydrolyze imide bonds and share six blocks of highly homologous amino acid sequences. We have found that guinea pig lung and kidney forms of aminopeptidase P, both forms bound to membranes via glycosyl phosphatidylinositol lipid anchors, share at least three of the six conserved blocks of amino acid sequences. In addition, aminopeptidase P acts as an aminoacylproline hydrolase and thus appears to be a member of the proline peptidase family.

Amino Acid Sequence↗

PubMed1999

Cloning and analysis of the gene for the human puromycin-sensitive aminopeptidase.

The gene encoding the human puromycin-sensitive aminopeptidase (PSA) has been cloned and characterized. The human PSA gene is composed of 23 exons and 22 introns and spans approximately 40 kb of chromosome 17 at the interval 17q12-21. An analysis of the 5' end of the human PSA transcript reveals that the translational start site corresponds to nt 210 of the human PSA cDNA, as suggested by RT-PCR, 5' RACE, and computer analysis of expressed sequence tags. A comparison of the exon/exon boundaries of the human PSA gene with those of the human aminopeptidase N (APN) gene shows little conservation, suggesting that the two genes, which are closely related in protein sequence, diverged early during evolution.

Amino Acid Sequence↗

PubMed2001

Wild-type and mutated nicastrins do not display aminopeptidase M- and B-like activities.

Nicastrin is a recently discovered protein interacting with presenilins and the beta-amyloid precursor protein, the proteins playing key roles in Alzheimer's disease and which, when mutated, appear responsible for early-onset familial forms of Alzheimer's disease. Nicastrin was reported to modulate beta-amyloid production, a phenotype affected differently by missense mutations or deletions of a conserved hydrophilic domain. In addition to such a function, nicastrin was recently suggested to possess putative catalytic activity based on its sequence homology with enzymes of the aminopeptidase family. We set up stably transfected human HEK293 cells expressing either wild-type or mutated nicastrins and we show that these proteins do not exhibit aminopeptidase M- and B-like activities.

Alzheimer Disease↗

PubMed2002

Active site of deblocking aminopeptidase from Pyrococcus horikoshii.

New hyperthermostable aminopeptidase from the hyperthermophilic archaeon Pyrococcus horikoshii has acylamino acid releasing (deblocking) activity for acyl (blocked) peptides. Such an enzyme can be used for N-terminal sequencing of acyl peptides. To clarify the active site of the deblocking aminopeptidase, we prepared three mutants in which one of the three possible active site amino acid residues (Asp or Glu) was replaced with their amide derivatives. Activity and cobalt ion dependence of these mutants were examined and compared with those of the native enzyme. The results suggest that all the three possible residues (Asp173, Glu205, and Glu206) participate in the catalytic activity through binding with the cobalt ion.

Amino Acid Sequence↗

PubMed1993

Degradation of enkephalins by rat lymphocyte and purified rat natural killer cell surface aminopeptidases.

Enkephalins have been reported to induce an elevation in natural killer (NK) cell cytolytic function. In the central nervous system, the short-lasting biological activity of the enkephalins may be attributable to their rapid hydrolysis at the cell surface. In a similar manner, a potential mechanism for regulating the effects of enkephalins on NK cells is through their degradation at the cell surface. The purpose of this study was to determine if NK cells were capable of enzymatically degrading Met- and Leu-enkephalin and to determine the type(s) of enzymes responsible. We report that rat nylon wool enriched splenocytes, purified NK cells, and interleukin-2 activated NK (A-NK) cells were capable of hydrolyzing the N-terminal Tyr residue from Met- and Leu-enkephalin as determined by high-performance liquid chromatography. The rate of Tyr cleavage from Met-enkephalin was approximately twice that of Leu-enkephalin for both splenocytes, NK, and A-NK cells. On a cellular basis, enkephalin degradation was four to five times greater with A-NK cells than with splenocytes. Only a Tyr cleavage product was detected, which suggested the possibility of an aminopeptidase activity. This was confirmed by the ability of bestatin, a specific inhibitor of cell surface aminopeptidases, to almost completely inhibit enkephalin degradation by splenocytes (85%) and A-NK cells (96%). A-NK cells were more sensitive to bestatin inhibition as indicated by their IC50 values (0.01 mM for splenocytes and 0.001 mM for A-NK cells). In addition, the chelator 1,10-phenanthroline was also capable of effectively inhibiting enkephalin degradation, suggesting that the enzyme responsible has the characteristics of a metalloprotease. In contrast to the effects of bestatin or phenanthroline, typical inhibitors of serine and thiol proteases were without effect.

Amino Acid Sequence↗

PubMed1994

Expression of the aminopeptidase N (CD13) gene in the human T cell lines HuT78 and H9.

The membrane-bound metalloprotease aminopeptidase N (APN, CD13, EC 3.4.11.2) is a well-established marker of normal and malignant cells of the myelomonocytic lineages. It is also expressed by leukemic blasts of a small group of patients suffering from acute or chronic lymphoid leukemia. CD13-specific monoclonal antibodies do not bind to the surface of normal B lymphocytes and APN-mRNA was not detectable by Northern analysis in normal lymphocytes or in T cell lines. A recent paper, however, describes the expression of CD13 on concanavalin A-stimulated T cells. Here, by means of enzymatic amplification of cDNA, cloning and sequencing of amplified cDNA fragments, in situ hybridization, and transcription start site mapping, evidence is provided that the human T cell lines HuT78 and H9 do contain APN-mRNA. Ala-pNA-hydrolyzing activity was detected in viable cells and cell homogenates as well as in size-fractionated protein fractions. Alanine-beta-naphthylamide (Ala-beta NA)-hydrolyzing activity was readily detectable after isoelectric focusing and blotting and was shown to be localized exclusively intracellularly in both cell lines. Usage of aminopeptidase-specific effectors revealed this activity to be distinct from CD13.

Aminopeptidases↗

PubMed1992

Aminopeptidase P: purification of a membrane-bound bradykininase from rat lung.

Aminopeptidase P that hydrolyzes the Arg1-Pro2-bond of bradykinin was solubilized from rat lung microsomes using phosphatidylinositol-specific phospholipase C. The enzyme was purified 420-fold by chromatography on decylagarose (two steps), omega-aminodecyl-agarose and DEAE-Sephacel. A single stained band was observed following native gradient (4-15%) polyacrylamide gel electrophoresis. Dipeptidylaminopeptidase IV-like activity was also present in the final preparation and co-migrated with aminopeptidase P in the above gel system.

Aminopeptidases↗

PubMed1981

Aminopeptidase N is a marker for the apical pole of porcine thyroid epithelial cells in vivo and in culture.

An aminopeptidase N has been detected by immunofluorescence in the apical plasma membrane of porcine thyroid cells, facing the follicular lumen. Freshly isolated cells obtained by tissue trypsinization, lose their polarity and exhibit a homogeneous enzyme distribution over the whole plasma membrane. In thyrotropin-stimulated cultured cells organized into follicles, the enzyme is localized the apical cell pole. In monolayer cells, on the other hand, the enzyme is distributed over the whole surface facing the medium. In both types of cultures fluorescence is also observed in intracytoplasmic organelles. In vivo, aminopeptidase ia a marker of the apical part of the thyroid plasma membrane, but its in vitro localization depends upon cell differentiation related to the culture conditions.

Aminopeptidases↗

PubMed1982

Fusion of the lac genes to the promoter for the aminopeptidase N gene of Escherichia coli.

Strains of Escherichia coli K12 were isolated in which the lac structural genes were fused to the promoter for the aminopeptidasee N structural gene (pepN). Although this enzyme is constitutively produced, the differential rate of synthesis is increased about 4-fold upon phosphate starvation. The pepN-lac fusions were shown to respond to phosphate specific regulatory signals. A plaque forming lambda transducing phage bearing the pepN-lac fusion was isolated. This phage was used to prove genetically the fusion of lac genes to the promoter for the aminopeptidase. These results demonstrate a control at the transcriptional level of aminopeptidase synthesis.

Aminopeptidases↗

PubMed1976

Conclusions about aminopeptidase in tissue sections from studies of amino acid naphthylamide hydrolysis.

Catalytic properties (KM, Vmax) of aminopeptidase in pig kidney sections, in isolated membranes and in a solubilized purified form were investigated using amino acid 2-naphthylamides and 4-methoxy-2-naphthylamides. In the first case these properties were estimated on the basis of the stain intensity resulting from the coupling of product with Fast Blue B, in the latter two cases they were measured fluorometrically. The following observations were made: (1) In all three cases the substrate turnover was shown to be a direct function of time and enzyme concentration. (2) The values obtained for the solubilized and the membrane bound form were practically identical but differed from those found in tissue sections. (3) Each amino acid derivative had defined constants, but these were difficult to obtain in sections, especially if it was necessary, on account of poor solubilities, to use low substrate concentrations. (4) Hydrophilic amino acid derivatives were adsorbed to tissue membranes much less than hydrophobic ones. (5) Fast Blue B caused a non-competitive inhibition of enzymic activity. (6) Binding of antibody against pure aminopeptidase caused inhibition of the enzymic hydrolysis of all the naphthylamides. Thus, histochemical stain intensities per time and area derived from one substrate at a defined concentration are suitable for the determination of enzyme concentrations. However, no conclusions regarding the homogeneity of the enzyme in sections can be drawn by comparing the stain intensities obtained with different substrates in contrast to data from the inhibition of substrate hydrolysis by antibody.

Amides↗