Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.11 (CD10)
 9,792 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antibodies raised in rabbits to detergent-solubilized pig kidney microvillar proteins have been used to investigate the membrane hydrolases by crossed immunoelectrophoresis. Eight enzymes were detected by specific staining methods: aminopeptidase M, dipeptidylpeptidase IV, neutral endopeptidase, aminopeptidase A, carboxypeptidase P, gamma-glutamyltransferase, trehalase and phosphodiesterase I. The mobility of all these enzymes, with the exception of trehalase and neutral endopeptidase, was increased by treatment of the detergent-solubilized preparation with papain. The difference between the detergent and proteinase forms of these enzymes is attributed to the removal of a small, non-antigenic peptide to which detergent is bound in significant quantities. This interpretation was further supported by experiments in which the microvillus fraction was labelled with an intramembrane photolabelling reagent, 1-azido-4-[125I]iodobenzene. After photolysis, the radioactivity in the membrane could be solubilized by detergent treatment but not by papain treatment. Radioautography after crossed charge-shift immunoelectrophoresis showed a good correlation between charge-shift (signifying the presence of detergent bound to a hydrophobic domain) and the presence of the label.
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PMID:Proteins of the kidney microvillar membrane. Immunoelectrophoretic analysis of the membrane hydrolases: identification and resolution of the detergent- and proteinase-solubilized forms. 48 90

The effects of a range of metallopeptidase inhibitors on the activities of the porcine kidney cell surface zinc aminopeptidases, aminopeptidase A (AP-A; EC 3.4.11.2), aminopeptidase N (AP-N; EC 3.4.11.7) and aminopeptidase W (AP-W; EC 3.4.11.16), have been directly compared. Amastatin and probestin were effective against all three aminopeptidases, with the concentration of inhibitor required to cause 50% inhibition (I50) in the low micromolar range (I50 = 1.5-20 microM), except for probestin with AP-N which displayed an I50 of 50 nM. Actinonin failed to inhibit significantly either AP-A or AP-W, and thus can be considered a relatively selective inhibitor (I50 = 2.0 microM) of AP-N. In contrast, bestatin was a relatively poor inhibitor of AP-N (I50 = 89 microM) and failed to inhibit AP-A, but was more potent towards AP-W (I50 = 7.9 microM). Thus, some of the observed chemotherapeutic actions of bestatin may be due to inhibition of cell-surface AP-W. A number of other metallopeptidase inhibitors, including inhibitors of endopeptidase-24.11 (EC 3.4.24.11) and membrane dipeptidase (EC 3.4.13.11), and the carboxylalkyl and phosphoryl inhibitors of angiotensin converting enzyme (EC 3.4.15.1) failed to inhibit significantly AP-A, AP-N or AP-W. However, AP-W was inhibited with I50 values in the micromolar range by the sulphydryl converting enzyme inhibitors rentiapril (I50 = 1.6 microM), zofenoprilat (I50 = 7.0 microM) and YS 980 (I50 = 17.7 microM). Neither AP-A nor AP-N were affected by these sulphydryl compounds. Inhibition of AP-W may account for some of the side effects noted with the clinical use of the sulphydryl converting enzyme inhibitors. The availability of compounds which are totally selective for AP-W over any of the other mammalian cell surface zinc aminopeptidases may aid in identifying endogenous substrates, and thus physiological or pathophysiological role(s) of AP-W.
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PMID:Inhibition of aminopeptidases N, A and W. A re-evaluation of the actions of bestatin and inhibitors of angiotensin converting enzyme. 136 Feb 11

Aminopeptidase inhibitors have been demonstrated to enhance the behavioral effects of both exogenously applied and endogenously released neuropeptides. In this study peptidase inhibitors were used as probes for involvement of central neuropeptides in osmotically-induced drinking behavior. Intracerebroventricular (i.c.v.) injections of amastatin, an aminopeptidase A inhibitor, potentiated water intake induced by subcutaneous injections of hypertonic saline. Drinking responses to i.c.v. infusions of hypertonic saline were also enhanced when amastatin was added to the infusions. The effect was not attenuated by the angiotensin receptor antagonist, [Sar1, Thr8]angiotensin II, which suggests that angiotensins do not play a role in the over-drinking. Drinking responses to centrally infused hypertonic saline were not enhanced by i.c.v. thiorphan, an endopeptidase inhibitor; this provides evidence that the effects of amastatin are specific for a particular class of peptidases. These results suggest that there is a role for an endogenous, non-angiotensinergic brain peptide in the mediation of osmotic thirst.
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PMID:Amastatin potentiates drinking elicited by osmotic stimuli: evidence for peptidergic mediation of intracellular dehydration-induced thirst. 142 35

A comprehensive survey of 11 peptidases, all of which are markers for renal microvillar membranes, has been made in membrane fractions prepared from pig choroid plexus. Two fractionation schemes were explored, both depending on a MgCl2-precipitation step, the preferred one having advantages in speed and yield of the activities. The specific activities of the peptidases in the choroid-plexus membranes were, with the exception of carboxypeptidase M, lower than in renal microvillar membranes: those of aminopeptidase N, peptidyl dipeptidase A ('angiotensin-converting enzyme') and gamma-glutamyltransferase were 3-5-fold lower, those of aminopeptidase A and endopeptidase-24.11 were 12-15 fold lower, and those of dipeptidyl peptidase IV and aminopeptidase W were 50-70-fold lower. Carboxypeptidase M had a similar activity in both membranes. Alkaline phosphatase and (Na+ + K+)-activated ATPase were more active in the choroid-plexus membranes. No activity for microsomal dipeptidase, aminopeptidase P and carboxypeptidase P could be detected. Six of the peptidases and (Na+ + K+)-activated ATPase were also studied by immunoperoxidase histochemistry at light- and electron-microscopic levels. Endopeptidase-24.11 and (Na+ + K+)-activated ATPase were uniquely located on the brush border, and the other two peptidases appeared to be much more abundant on the endothelial lining of microvessels. Dipeptidyl peptidase IV and aminopeptidase W were also detected in microvasculature. Pial membranes associated with the brain and spinal cord also stained positively for endopeptidase-24.11, aminopeptidase N and peptidyl dipeptidase A. The immunohistochemical studies indicated the subcellular fractionation did not discriminate between membranes derived from epithelial cells (i.e. microvilli) and those from endothelial cells. The possible significance of these studies in relation to neuropeptide metabolism and the control of cerebrospinal fluid production is discussed.
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PMID:Membrane peptidases in the pig choroid plexus and on other cell surfaces in contact with the cerebrospinal fluid. 265 79

Porcine cerebral microvessels were isolated by differential sieving and centrifugation and were characterized by microscopic examination and marker enzyme enrichment (gamma-glutamyltransferase; EC 2.3.2.2). Purified microvessels contained a membrane-bound enzyme immunologically indistinguishable from renal aminopeptidase A (AmA; EC 3.4.11.7). AmA hydrolyzed both alpha-glutamyl- and alpha-aspartyl-2-naphthylamide, and hydrolysis was competitively inhibited by angiotensin II. Micro-vessel AmA hydrolyzed the N-terminal Asp1-Arg2 bond of both angiotensin I and angiotensin II, whereas the angiotensin II antagonist saralasin [(Sar1, Ala8)angiotensin II] was resistant to N-terminal hydrolysis. Angiotensin metabolism was optimal at pH 8.5 and was inhibited by EDTA, o-phenanthroline and amastatin. Conversely, inhibitors of neutral endopeptidase (phosphoramidon), post-proline cleaving enzyme (Z-Pro-Prolinal), carboxypeptidase N [D-L-mercaptomethyl-3-guanidinoethylthiopropanoic acid (MERGETPA)] and angiotensin I converting enzyme (captopril) had no effect. The Km values of angiotensin I, angiotensin II and (Asn1, Val5)angiotensin II for microvessel AmA were 40.1 +/- 8.2, 35.3 +/- 4.3 and 156 +/- 22 microM respectively. Cerebral microvascular aminopeptidase A may play a role in vivo in modulating angiotensin-mediated local cerebral blood flow, and in preventing circulating angiotensins from crossing the blood-brain barrier.
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PMID:Angiotensin metabolism by cerebral microvascular aminopeptidase A. 289 20

Five membrane peptidases were studied by radiation inactivation analysis of pig kidney microvillar membranes. One heterodimeric enzyme, gamma-glutamyl transferase, presented a target size corresponding to the dimeric Mr. The other enzymes are known to be homodimers. Three of these, aminopeptidase A. aminopeptidase N and dipeptidyl peptidase IV, gave results clearly indicating the monomer to be the target and, hence, in this group the association of the subunits was not essential for activity. The target size for endopeptidase-24.11 was intermediate between those for monomer and dimer and its functional state was not resolved by the experiments.
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PMID:Radiation inactivation analysis of kidney microvillar peptidases. 352 52

Microvilli from human placental syncytiotrophoblast are rich in angiotensin I converting enzyme (ACE), aminopeptidase A, a carboxypeptidase N-like enzyme, and a neutral endopeptidase (NEP). The specific activities of these enzymes were enhanced in microvillus-enriched fractions obtained by differential centrifugation: Purified microvilli were isolated in a discontinuous sucrose gradient. The placental microvilli hydrolyzed angiotensin II, vasopressin and oxytocin as shown by high pressure liquid chromatography. The inhibitors, bestatin, phosphoramidon, and o-phenanthroline, established the specificity of the enzymes. Aminopeptidase A (angiotensinase A) cleaved angiotensin II to angiotensin III and Asp1. NEP from placenta and from human kidney hydrolyzed oxytocin at the Pro7-Leu8 bond to yield oxytocin 1-7 and leucyl-glycine amide, but did not hydrolyze vasopressin. Vasopressin was cleaved by aminopeptidases in the placental membranes. On electroblotting placental NEP appeared as a double band with a molecular weight slightly higher than the 90,000 of the purified kidney enzyme. Neuraminidase treatment reduced the molecular weight of the placental enzyme to approximately 90,000, indicating that it contains a large amount of sialic acid. The microvilli of human placenta are thus rich in enzymes that may regulate passage of peptides at the maternal-fetal interface.
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PMID:Enzymes in placental microvilli: angiotensin I converting enzyme, angiotensinase A, carboxypeptidase, and neutral endopeptidase ("enkephalinase"). 609 76

An organ culture employing slices of renal-cortex tissue from piglets of the Yucatan strain was used to study the biogenesis of four microvillar peptidases: endopeptidase-24.11 (EC 3.4.24.11), dipeptidyl peptidase IV (EC 3.4.14.5), aminopeptidase N (EC 3.4.11.2) and aminopeptidase A (EC 3.4.11.7). The viability of the culture system was confirmed by the preservation of ultrastructural integrity and by an unchanged uptake of [3H]alanine into cells during the period of the experiments. After labelling with [35S]methionine, treatment with Mg2+ yielded two fractions, one containing microvilli and another, the Mg2+ pellet, containing intracellular and basolateral membranes. The labelled forms of the peptidases, isolated by immunoprecipitation, were analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and fluorography. The Mg2+ pellet contained the earliest detectable forms of the enzymes. In each case, a polypeptide of lower Mr than the mature form and sensitive to treatment with endo-beta-N-acetylglucosaminidase H was the first form to be detected. These high-mannose forms were followed, about 30 min after the pulse, by a complex glycosylated form of higher Mr. Only the latter form was observed in microvilli and then only after 90 min of the chase period. A quantitative study of dipeptidyl peptidase IV showed that the forms observed in the Mg2+ pellet were precursors of those in the microvillar fraction. No labelled forms were observed in the cytosol. All four peptidases were thus synthesized within membrane compartments and glycosylated in two steps before assembly in microvilli.
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PMID:Proteins of the kidney microvillar membrane. Biosynthesis of endopeptidase-24.11, dipeptidylpeptidase IV and aminopeptidases N and A in pig kidney slices. 615 93

Pig kidney microvillar proteins were extracted with octyl beta-glucoside and reconstituted in liposomes prepared from microvillar lipids of known composition. Four peptidases, namely endopeptidase (EC 3.4.24.11), aminopeptidases N (EC 3.4.11.2) and A (EC 3.4.11.7) and dipeptidyl peptidase IV (EC 3.4.14.5), were shown to be reconstituted. At lipid/protein ratios greater than 4:1, about half the detergent-solubilized protein and nearly all of the activity of the four peptidases were reconstituted. Dissolution of the liposomes with Triton X-100 did not increase the activity of any of these peptidases, a result consistent with an asymmetric, 'right-side-out', orientation of these enzymes. When purified, endopeptidase was subjected to the same procedure; the two amphipathic forms of the enzyme (the detergent form and the trypsin-treated detergent form) were fully reconstituted. The amphiphilic form, purified after toluene/trypsin treatment, failed to reconstitute. Electron microscopy of microvilli showed that the appearance of the surface particles was profoundly altered by treatment with papain. Before treatment, the microvilli were coated with particles of stalk lengths ranging from 2.5 to 9 nm. After papain treatment nearly all the particles had stalks of 2-3 nm. Reconstituted microvillar proteins in liposomes showed the same heterogeneity of stalk length. In contrast, liposomes containing reconstituted endopeptidase revealed a very homogeneous population of particles of stalk length 2 nm. Since the smallest dimension of a papain molecule is 3.7 nm, the ability of papain, and other proteinases of similar molecular size, to release microvillar enzymes is crucially affected by the length of the junctional peptide that constitutes the stalk of this type of membrane protein.
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PMID:Proteins of the kidney microvillar membrane. Reconstitution of endopeptidase in liposomes shows that it is a short-stalked protein. 634 16

The usefulness of optimized and newly elaborated histochemical methods for proteinases is illustrated on two selected substances. DAP IV (Gly-Pro-MNA,FBB,pH 7.2) was discovered in 39% and DAP II (Lys-Ala-MNA,FBB,pH 5.5) in 60% of the lymphocytes of human peripheral blood (ly). The reaction product of such ly differs in quality and quantity. On the ultrastructural level, the reaction product of DAP IV (Gly-Pro-MNA,HNF) was found in cell membranes and lysosomes. Enzyme activity in other areas was probably suppressed during the preparation procedure. Although the number of ly revealed with Lys-Pro-MNA and Phe-Pro-MNA at pH 5.5 and with Lys-Pro-MNA at pH 7.2 is high, these substrates do not distinctly discriminate DAP IV and DAP II. DAP IV occurs exclusively in T lymphocytes. The number of DAP IV-positive ly was not decreased in patients with myelofibrosis, plasmacytoma, chronic granulocytic leukemia, or tricholeukemia. It was, however, greatly reduced in chronic lymphatic leukemia (CLL). In patients with malignant lymphomas other than CLL, ly presence is related to the stage of the disease. Decreased values indicate a more severe stage or a relapse. In the majority of patients with gastric cancer DAP IV-positive ly were decreased. They were normal or increased in patients with peptic ulcer. The assessment of the number of DAP IV-positive ly is a simple method that provides information regarding the condition of patients with malignant lymphomas and gastric carcinoma. Neutrophilic leukocytes and their precursors, and to a lesser extent monocytes, are revealed when N-acetyl-Met-I-naphthyl ester (Ac-Met-N) is used as substrate. Membrane-bound lysosomal and cytosol proteinases were investigated together with disaccharidases in jejunal biopsies of patients with malabsorption syndrome. Activities of all enzymes were affected in patients with celiac disease. According to their impairment enzymes could be arranged: Lactase(L). trehalase (T), brush border endopeptidase (BBEP), gamma-glutamyl transferase (GGT), DAP IV, enzyme(s) cleaving Ac-Mer-N, aminopeptidase A, cytosol peptidases and aminopeptidase M. In the propria, DAP IV is decreased or absent, while GGT and, particularly, DAP II are increased. After a gluten-free diet, activities are restored in a reverse order. BBEP and GGT are useful as auxiliary parameters in the assessment of the damage or differentiation degree of enterocytes. DAP IV is a sensitive indicator of the involvement of the propria.
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PMID:Proteinases in pathology. Usefulness of histochemical methods. 701 84


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