Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.15.1 (ACE)
18,300 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The property of solutions of Triton X-114 to separate into detergent-rich and detergent-poor phases at 30 degrees C has been exploited to investigate the identities of the aminopeptidases in synaptic membrane preparations from pig striatum. When titrated with an antiserum to aminopeptidase N (EC 3.4.11.2), synaptic membranes solubilized with Triton X-100 revealed that this enzyme apparently comprises no more than 5% of the activity releasing tyrosine from [Leu]enkephalin. When assayed in the presence of puromycin, this proportion increased to 20%. Three integral membrane proteins were fractionated by phase separation in Triton X-114. Aminopeptidase activity, endopeptidase-24.11 and peptidyl dipeptidase A partitioned predominantly into the detergent-rich phase when kidney microvillar membranes were so treated. However, only 5.5% of synaptic membrane aminopeptidase activity partitioned into this phase, although the other peptidases behaved predictably. About half of the aminopeptidase activity in the detergent-rich phase could now be titrated with the antiserum, showing that aminopeptidase N is an integral membrane protein of this preparation. Three aminopeptidase inhibitors were investigated for their ability to discriminate between the different activities revealed by these experiments. Although amastatin was the most potent (IC50 = 5 X 10(-7) M) it failed to discriminate between pure kidney aminopeptidase N, the total activity of solubilized synaptic membranes and that in the Triton X-114-rich phase. Bestatin was slightly more potent for total activity (IC50 = 6.3 X 10(-6) M) than for the other two forms (IC50 = 1.6 X 10(-5) M). Puromycin was a weak inhibitor, but was more selective. The activity of solubilized membranes was more sensitive (IC50 = 1.6 X 10(-5) M) than that of the pure enzyme or the Triton X-114-rich phase (IC50 = 4 X 10(-4) M). We suggest that the puromycin-sensitive aminopeptidase activity that predominates in crude synaptic membrane preparations may be a cytosolic contaminant or peripheral membrane protein rather than an integral membrane component. Aminopeptidase N may contribute to the extracellular metabolism of enkephalin and other susceptible neuropeptides in the brain.
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PMID:The metabolism of neuropeptides. Phase separation of synaptic membrane preparations with Triton X-114 reveals the presence of aminopeptidase N. 286 52

Endopeptidase-24.11 (sometimes referred to as 'enkephalinase') is a key cell-surface enzyme in the metabolism of neuropeptides. A previous immunohistochemical study mapped the enzyme in pig brain and indicated a striosomal ordering of the enzyme within the striatum. This point has now been confirmed by staining adjacent sections for acetylcholinesterase (by histochemistry) and endopeptidase-24.11 (by an immunoperoxidase method). While there were some general similarities in the mapping of these two hydrolases, e.g. in the caudate-putamen, globus pallidus, olfactory tubercle, substantia nigra and striatonigral tract, there were differences in intensity and in the microscopic distribution, e.g. as in striosomes for which acetylcholinesterase was diminished. Two other membrane peptidases, peptidyl dipeptidase A ('angiotensin converting enzyme') and aminopeptidase N, were also mapped by the same immunohistochemical method. Peptidyl dipeptidase A had some similarities with endopeptidase-24.11, e.g. in its concentration within the striatal nuclei, but clear differences were also apparent, in particular the absence of staining of the former in the globus pallidus and olfactory tubercle. Immunostaining for aminopeptidase N, in contrast to the other peptidases, was observed as a diffuse staining throughout the gray matter. At the microscopic level, two important differences were that staining for aminopeptidase N and peptidyl dipeptidase A was very intense throughout the vasculature of the brain and that striatal efferent bundles of unmyelinated fibres staining positively for endopeptidase-24.11 were depleted of the other two peptidases. All three peptidases were identified in the pia mater. Thus, endopeptidase-24.11, unlike peptidyl dipeptidase A and aminopeptidase N, is a marker for a set of striatal efferent fibres in pig brain.
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PMID:Endopeptidase-24.11 is striosomally ordered in pig brain and, in contrast to aminopeptidase N and peptidyl dipeptidase A ('angiotensin converting enzyme'), is a marker for a set of striatal efferent fibres. 290 57

The major site of hydrolysis was the Gly8-Leu9 bond. Angiotensin converting enzyme (peptidyl dipeptidase A, EC 3.4.15.1) from pig kidney hydrolysed substance P releasing the C-terminal tripeptide Gly-Leu-MetNH2 but failed to hydrolyse neurokinin B. Pig brain striatal synaptic membranes hydrolysed neurokinin B producing a similar pattern of products as did endopeptidase-24.11. Substantial inhibition of this activity was achieved with the selective inhibitor phosphoramidon. A combination of phosphoramidon and bestatin abolished the hydrolysis of neurokinin B by synaptic membranes. Thus, a bestatin-sensitive aminopeptidase may play a role in the synaptic metabolism of neurokinin B in addition to endopeptidase-24.11. This aminopeptidase appears to be distinct from aminopeptidase N (EC 3.4.11.2).
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PMID:Neurokinin B is hydrolysed by synaptic membranes and by endopeptidase-24.11 (enkephalinase) but not by angiotensin converting enzyme. 299 26

Both the sulphated and non-sulphated forms of cholecystokinin (CCK) octapeptide are susceptible to hydrolysis by the cell-surface peptidases endopeptidase-24.11 (NEP), angiotensin converting enzyme and aminopeptidase N (AP-N). Indirect studies have previously implicated an elastase-like serine endopeptidase in CCK metabolism in brain. We have therefore compared the hydrolysis of CCK, in both sulphated and non-sulphated forms by solubilized membrane preparations from the human astrocytoma clone D384 and the neuroblastoma line SH-SY5Y. Selective peptidase inhibitors were used to elucidate the principal activities involved in CCK metabolism. In the glial cell line the hydrolysis of cholecystokinin octapeptide (CCK-8), sulphated or non-sulphated, was inhibited predominantly by the NEP inhibitor, phosphoramidon (PR). In contrast, in the neuroblastoma line, angiotensin converting enzyme (ACE) was seen to play a major role in metabolism of CCK-8 with a lesser effect attributable to NEP but with some differences between sulphated and non-sulphated forms reflecting the preference of ACE for CCK-8ns. In neither cell line was a significant effect of the serine peptidase inhibitor Dip-F seen on CCK metabolism arguing against the presence of a putative CCK-degrading serine peptidase in these cell lines. Both NEP and ACE remain as candidates for inactivation of CCK at the cell surface.
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PMID:Comparison of cholecystokinin metabolism by membrane preparations from the human astrocytoma clone D384 and the neuroblastoma line SH-SY5Y. 791 87

The cell-surface expression of endopeptidase-24.11 (EC 3.4.24.11) on Caco-2 cells cultured to confluency is markedly heterogeneous unlike that of dipeptidylpeptidase IV (EC 3.4.14.5). Here we have investigated the cell-surface expression of three other ectopeptidases: angiotensin converting enzyme (EC 3.4.15.1), aminopeptidase N (EC 3.4.11.2) and aminopeptidase W (EC 3.4.11.16). We show by indirect immunofluorescent staining that these three enzymes are present on the surface of some cells but not on others. However, these enzymes were detected in the majority of detergent-permeabilised Caco-2 cells indicating the presence of intracellular pools of these enzymes. This suggests that there may either be differential regulation of apical transport for these peptidases or that they recycle at different rates.
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PMID:Mosaic expression of membrane peptidases by confluent cultures of Caco-2 cells. 809 58

Neutral endopeptidase (NEP; also known as neprilysin and enkephalinase; EC 3.4.24.11) is a cell-surface metallopeptidase that is present in many mammalian tissues. It is particularly abundant on the brush-border membranes of the kidney proximal tubule. In this paper, the presence of NEP in purified glomeruli from dog kidney was assessed by measuring phosphoramidon- and thiorphan-sensitive [D-Ala2,Leu5]enkephalin-degrading activity. Using this assay, the Km and kcat. of the glomerular enzyme were found to be identical to those of the tubular enzyme. By Western blotting the apparent M(r) of the glomerular enzyme was found to be 104,000, compared with 94,000 for the tubular enzyme. This might be due to a different glycosylation pattern, since endoglycosidase F treatment of NEP obtained from both tissues yielded deglycosylated enzymes with similar electrophoretic mobilities. The glomerular enzyme also appears to be membrane-bound, since it was retained in the detergent-rich phase after phase separation with Triton X-114. Autoradiography experiments performed with RB104, a new highly selective and potent NEP inhibitor, showed that NEP was expressed in both glomeruli and proximal tubules. The presence in glomeruli of NEP and some other brush-border peptidases (dipeptidyl-dipeptidase IV, aminopeptidase N and angiotensin I-converting enzyme) suggests that cell-surface peptidases might play an important role as regulators of plasma-derived peptides in this part of the nephron.
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PMID:Characterization of neutral endopeptidase 24.11 in dog glomeruli. 848 5

The biologically active vasoactive peptides, the endothelins (ETs), are generated from inactive intermediates, the big endothelins, by a unique processing event catalysed by the zinc metalloprotease, endothelin converting enzyme (ECE). In this overview we examine the actions of endothelins in the brain, and focus on the structure and cellular locations of ECE. The heterogeneous distribution in the brain of ET-1, ET-2, and ET-3 is discussed in relation to their hemodynamic, mitogenic and proliferative properties as well as their possible roles as neurotransmitters. The cellular and subcellular localization of ECE in neuronal and in glial cells is compared with that of other brain membrane metalloproteases, neutral endopeptidase-24.11 (neprilysin), angiotensin converting enzyme and aminopeptidase N, which all function in neuropeptide processing and metabolism Unlike these ectoenzymes, ECE exhibits a dual localisation in the cell, being present on the plasma membrane and also, in some instances, being concentrated in a perinuclear region. This differential localization may reflect distinct targeting of different ECE isoforms, ECE-1 alpha, ECE-1 beta, and ECE-2.
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PMID:The endothelin system and endothelin-converting enzyme in the brain: molecular and cellular studies. 923 59

The modulation of proteolytic activity is an important factor in regulating the metabolism and function of peptide hormones. In this study, the activities of dipeptidyl (carboxy)peptidase (angiotensin-converting enzyme [ACE]), aminopeptidase N (APN), and dipeptidyl (amino)peptidase IV (DPP IV) were measured in the blood, the human bronchial epithelial and alveolar cells, bronchoalveolar macrophages, and the soluble phase of bronchoalveolar lavage (BAL) samples obtained from normal human volunteers and patients with pulmonary pathologic conditions. BAL fluid expressed ACE activity and very low levels of APN and DPP IV activities in the volunteer population, but higher levels could be measured in samples from patients. In patients, increased APN corresponded to a high granulocyte count, while DPP IV and ACE were associated with a high percentage of lymphocytes. Neither AIDS nor smoking induced an increased level of these enzymes. Immunohistochemical staining of bronchoalveolar smears with anti-human ACE monoclonal antibody showed that only macrophages expressed this enzyme. Enzyme histochemistry for DPP IV and APN showed that all leukocytes expressed these activities. APN, DPP IV, and ACE activities were also found in cell extracts of bronchoalveolar macrophages. In extracts of bronchial epithelial and alveolar cells, only APN and DPP IV activities were detected. Kinetic properties of the soluble enzymes in lavage supernatants were comparable to those of serum enzymes. These results demonstrate that soluble forms of cellular enzymes found in BAL fluid are regulated independently of blood and that different cell types may release these enzymes.
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PMID:Peptidases in human bronchoalveolar lining fluid, macrophages, and epithelial cells: dipeptidyl (amino)peptidase IV, aminopeptidase N, and dipeptidyl (carboxy)peptidase (angiotensin-converting enzyme). 942 34

Four N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin are prepared and characterized. Their enzymatic and chemical stability are assessed using high-performance liquid chromatography. The prodrug derivatives are shown to degrade stoichiometrically to Leu-enkephalin in phosphate buffer [t1/2 (0.05 M phosphate buffer without KCl): acetone prodrug (II) 930 min; cyclopentanone prodrug (III): 216 min; cyclohexanone prodrug (IV): 432 min; 4-methylcyclohexanone prodrug (V): 792 min]. Furthermore, the prodrugs are shown to afford global stabilization of the Leu-enkephalin molecule towards the enzymes, aminopeptidase N and angiotensin converting enzyme, primarily responsible for degradation of Leu-enkephalin at the blood-brain barrier and in plasma. Therefore, the 4-imidazolidinones, being metabolic stable and bioreversible, may be suitable prodrug candidates for delivery of Leu-enkephalin to important target areas such as the brain, if given intravenously.
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PMID:N-terminal 4-imidazolidinone prodrugs of Leu-enkephalin: synthesis, chemical and enzymatic stability studies. 997 15

Through the development of a new chemical strategy, aminophosphinic peptides containing a pseudoglutamyl residue (Glu Psi(PO2-CH2)Leu-Xaa) in the N-terminal position were synthesized and evaluated as inhibitors of aminopeptidase A (APA). The most potent inhibitor developed in this study, Glu Psi(PO2-CH2)Leu-Ala, displayed a Ki value of 0.8 nM for APA, but was much less effective in blocking aminopeptidase N (APN) (Ki = 31 microM). The critical role of the glutamyl residue in this phosphinic peptide, both in potency and selectivity, is exemplified by the P1 position analogue, Ala Psi(PO2-CH2)Leu-Ala, which exhibited a Ki value of 0.9 microM toward APA but behaved as a rather potent inhibitor of APN (Ki = 25 nM). Glu Psi(PO2-CH2)Leu-Xaa peptides are poor inhibitors of angiotensin converting enzyme (Ki values higher than 1 microM). Depending on the nature of the Xaa residue, the potency of these phosphinic peptides toward neutral endopeptidase 24-11 varied from 50 nM to 3 microM. In view of the in vivo role of APA in the formation of brain angiotensin III, one of the main effector peptides of the renin angiotensin system in the central nervous system, highly potent and selective inhibitors of APA may find important therapeutic applications soon.
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PMID:Potent and selective inhibition of zinc aminopeptidase A (EC 3.4.11.7, APA) by glutamyl aminophosphinic peptides: importance of glutamyl aminophosphinic residue in the P1 position. 1065 62


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