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 susceptibility to hydrolysis of LHRH and the decapeptide analogue Antide has been compared. The hydrolysis of LHRH by pig kidney brush border membranes is inhibited by phosphoramidon (I50 = 5.6 nM) implicating endopeptidase-24.11 in the initiation of hydrolysis. Under conditions in which LHRH is fully degraded by brush border membranes, Antide was completely resistant to hydrolysis. Similar results were obtained with purified preparations of both endopeptidase-24.11 and angiotensin converting enzyme. These data confirm that the remarkable duration of action of Antide is due principally to its stability to hydrolysis by cell-surface peptidases.
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PMID:Metabolic stability of the LHRH antagonist antide to cell-surface peptidases. 201 20

Angiotensin I converting enzyme (kininase II; ACE) has been described as a peptidyldipeptidase or dipeptidyl carboxypeptidase (EC 3.4.15.1) of the pulmonary endothelial cells, which liberates angiotensin II or inactivates kinins. However, ACE has a much wider distribution and substrate specifity; it is concentrated in human epithelial cells (e.g. brush border of the kidney, placenta, intestine and choroid plexus), neuroepithelial cells (subfornical organ, pallidonigral dendrites, median eminence) and male genital tract (testes, prostate, epididymides, seminal plasma). Its substrates include enkaphalins, the C-terminal extended proenkephalins and a protected chemotactic tripeptide. Recent, mostly in vitro studies with purified ACE, indicate that ACE also cleaves peptides by other than peptidyldipeptidase action. Homogeneous human ACE inactivated substance P in spite of its blocked C-terminus (Met11-NH2) primarily by releasing the C-terminal tripeptide. A blocked C-terminal tripeptide, Arg-Pro-Gly-NH2 was also released from the luteinizing hormone releasing hormone (LHRH). Although ACE shares many properties with carboxypeptidases, it surprisingly cleaves the N-terminal tripeptide greater than Glu1-His2-Trp3 from LHRH. Because human ACE hydrolyzes a variety of peptide hormones, actions of its inhibitors may go well beyond blocking the conversion of angiotensin I.
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PMID:The broad substrate specificity of human angiotensin I converting enzyme. 244 Jun 24

This study provides evidence that: 1) LHRH is degraded by renal brush border hydrolases, followed by reabsorption of oligopeptide metabolites in the proximal kidney tubule. 2) Peptide carriers are present in the luminal membrane of the proximal nephron, which apparently function to reabsorb oligopeptide metabolites resulting from hydrolysis of filtered peptides, including LHRH. 3) Renal brush border hydrolysis of LHRH involves cleavage at multiple sites by endopeptidases like angiotensin I-converting enzyme and endopeptidase 24.11; D-amino acid substituents at these sites may alter the expected cleavage pattern of the analogs. 4) A transcytotic pathway is present in the proximal nephron which is facilitated by endocytosis of cationic macromolecules; such a pathway may function to reabsorb hydrolytically resistant peptides, but the issue of potential toxicity must be clarified.
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PMID:Renal handling of luteinizing hormone releasing hormone: a model for peptide transport and hydrolysis. 283 70

The concentration of luteinizing hormone releasing hormone (LHRH) (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2), which reaches the anterior pituitary via the hypothalamo-hypophyseal portal system, appears to be controlled in part by the rate of LHRH degradation within the hypothalamus and/or pituitary. Specific, active site-directed endopeptidase inhibitors synthesized in our laboratory were used to identify the enzyme(s) involved in LHRH degradation by hypothalamic and pituitary membrane preparations, and by an intact anterior pituitary tumor cell line (AtT20). Incubation of LHRH with pituitary and hypothalamic membrane preparations led to the formation of pGlu-His-Trp (LHRH1-3) as the main reaction product. Under the same conditions, addition to the incubation mixtures of captopril, an inhibitor of the angiotensin converting enzyme, led to accumulation of pGlu-His-Trp-Ser-Tyr (LHRH1-5) and, to a lesser extent, pGlu-His-Trp-Ser-Tyr (LHRH1-6). The degradation of LHRH and the formation of the N-terminal tri- and pentapeptides was blocked by N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Phe-p-aminobenzoate (cFP-AAF-pAB), a specific, active site directed inhibitor of endopeptidase-24.15. Some inhibition of LHRH degradation and formation of the N-terminal hexapeptide was also obtained in the presence of N-[1-carboxy-2-phenylethyl]-Phe-p-aminobenzoate (cFE-F-pAB), an inhibitor of endopeptidase-24.11. Similar results were obtained with AtT20 cell membranes and with intact AtT20 cells in monolayer culture. Following cleavage by endopeptidases the C-terminal part of LHRH was rapidly degraded by aminopeptidases. Superactive analogs of LHRH in which Gly6 was replaced by a D-amino acid are resistant to degradation by both endopeptidase-24.11 and -24.15. In vivo, when LHRH was injected directly into the third ventricle of rats, the presence of cFP-AAF-pAB inhibited LHRH degradation. It is concluded that LHRH degradation is primarily initiated by the membrane-bound form of endopeptidase-24.15 to yield pGlu-His-Trp-Ser-Tyr and to a lesser extent by endopeptidase-24.11 to yield pGlu-His-Trp-Ser-Tyr-Gly.
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PMID:Endopeptidase-24.15 is the primary enzyme that degrades luteinizing hormone releasing hormone both in vitro and in vivo. 329 5

Less than Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, the luteinizing hormone-releasing hormone, LHRH, is degraded in renal proximal tubules (PT) in vivo (rat) and in vitro (rabbit) to less than Glu-His (2), less than Glu-His-Trp (3), and less than Glu-His-Trp-Ser (4). LHRH may be cleaved by endopeptidases simultaneously at multiple bonds, or initially at Ser4-Tyr5 followed by carboxypeptidase hydrolysis of 4 to 3 and then 2. To distinguish between these mechanisms, [3H]LHRH analogues were incubated with rabbit renal brush-border membranes (BBM), microinfused into PT in vivo or in vitro, and products were analyzed by HPLC. [D-Ser4]LHRH was not cleaved at D Ser4-Tyr5 but yielded less than Glu-His-Trp-D-Ser-Tyr-Gly as the major metabolite plus 2 and 3. [D-Trp6]LHRH was cleaved by BBM and PT to 2 and 3, but not to 4. [D-Ser4, D-Trp6]LHRH was not cleaved by BBM, but was degraded to 2 by PT in vivo. Thus, D-amino acid substituents altered the expected cleavage pattern of these analogues. [3H]LHRH was cleaved by BBM or by endopeptidase-24.11 from porcine PT to metabolites 2, 4, small amounts of 3, and less than Glu-His-Trp-Ser-Tyr-Gly, but cleavage was strongly inhibited by the specific inhibitor phosphoramidon. Thus, normally LHRH may be cleaved in PT by endopeptidase-24.11 to 2 and 4, and by angiotensin I-converting enzyme to 3, its known cleavage site.
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PMID:Effects of D-amino acid substituents on degradation of LHRH analogues by proximal tubule. 354 29

The capillary endothelial cells of the median eminence represent a potential site for the degradation/modification of both circulating and hypothalamic peptides passing through the hypophysial portal system toward the pituitary. This study examines endothelial cell peptidase expression in vitro by monitoring the metabolism of gonadotropin-releasing hormone (GnRH) by cultured endothelial cells from sheep median eminence. Cleavage of GnRH by median eminence endothelial cell membranes generated GnRH1-5 as the primary stable product, which was then degraded to GnRH1-3 and free amino acids. Degradation of GnRH was completely inhibited by TPCK, ZnCl2 and N-ethylmaleimide, and partially inhibited by EDTA and by a specific inhibitor of the metalloendopeptidase EC 3.4.24.15, CFP-AAY-pAB. Interestingly, an increase in GnRH1-9 production was seen with the latter inhibitors, suggesting a two-step mechanism of GnRH degradation involving a primary cleavage at the Pro9-Gly10-NH2 bond, inhibitable by TPCK, ZnCl2, and NEM, followed by cleavage by EC 3.4.24.15 to generate GnRH1-5. Phosphoramidon and angiotensin converting enzyme inhibitors (as well as other non-specific inhibitors) were without effect, indicating that endopeptidase EC 3.4.24.11 and angiotensin converting enzyme are not involved. Neither bovine aortic endothelial cell nor AtT-20 cell membranes exhibited this pattern of peptidase activity. Degradation of GnRH by intact median eminence endothelial cells in culture was also observed, suggesting an extracellular orientation for these enzymes; the potential role of such peptidases in the fine regulation of both pituitary function and local blood flow is currently under investigation.
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PMID:Characterization of membrane-associated peptidase activities expressed by endothelial cells of the ovine median eminence. 804 22

Pulmonary alveolar type I epithelial cell and its progenitor, type II cell, present major transport and enzyme barriers for systemic delivery of pulmonary administered peptide drugs. The present study investigates the effect of cellular differentiation of type II to type I cells on their proteolytic activities, and evaluates the suitability of a continuous lung cell line, A549, for drug transport and degradation studies. High performance liquid chromatography was used to assess the degradation kinetics of two model peptide substrates, luteinizing hormone releasing hormone (LHRH) and [D-Ala(6)10-fold decrease in proteolytic activities for LHRH, as compared to type II cells. The continuous lung cell line A549 formed leaky monolayers and exhibited similar enzyme activities to the primary type II cells. The responsible enzymes for degradation of LHRH in type II and A549 cells were angiotensin converting enzyme (ACE), EP24.11, and EP24.15. In contrast, no EP24.15 or ACE activity was observed in type I-like pneumocytes and only a weak EP24.11 activity was detected. In all cell types, the degradation rate of [D-Ala(6)]-LHRH was about 3-8 times lower than that of LHRH. This peptide analog was resistant to degradation by EP24.15 and EP24.11, but was susceptible to ACE-mediated cleavage.
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PMID:Characterization of proteolytic activities of pulmonary alveolar epithelium. 1067 87

The 94-kDa ram epididymal fluid form of the sperm membrane-derived germinal angiotensin I-converting enzyme (ACE) was purified by chromatography, and some of its enzymatic properties were studied. For the artificial substrate furanacryloyl-L-phenylalanylglycylglycine (FAPGG), the enzyme exhibited a Michaelis constant (K(m)) of 0.18 mM and a V(max) of 34 micromoles/(min x mg) and for hippuryl-L-histidyl-L-leucine a K(m) of 2.65 mM and a V(max) of 163 micromoles/(min x mg) under the defined standard conditions (300 mM NaCl and 50 mM Tris; pH 7.5 and 8.3, respectively). The FAPGG hydrolysis was decreased by 82.5% and 67.5% by EDTA and dithioerythritol, respectively, and was totally inhibited by specific ACE inhibitors such as captopril, P-Glu-Trp-Pro-Arg-Pro-Glu-Ile-Pro-Pro, and lisinopril. Optimum activity for FAPGG was with pH 6.0, 50 mM chloride, and 500 microM zinc. Under the various conditions tested, bradykinin, angiotensin (Ang) I, Ang II, and LHRH were competitors for FAPGG. Bradykinin and angiotensin I were the best competitors. The enzyme cleaved Ang I into Ang II, and the optimal conditions were with pH 7.5 and 300 mM chloride. The relationship between the carboxypeptidase activity in seminal plasma and the prediction of fertility of young rams was also studied. These results indicated a correlation between sperm concentration and ACE activity in semen but showed no statistically significant correlation between such activity and fertility of the animal. Finally, we tested the role of ACE in fertilization; no difference in the in vitro fertilization rate was observed in the presence of 10(-4) M captopril.
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PMID:Physiological and enzymatic properties of the ram epididymal soluble form of germinal angiotensin I-converting enzyme. 1167 47

Neuropeptide processing metalloenzymes, such as angiotensin converting enzyme, neprilysin, endothelin converting enzyme, neurolysin, and EC3.4.24.15 (EP24.15), are central to the formation and degradation of bioactive peptides. We present EP24.15 as a paradigm for novel functions ascribed to these enzymes in the neurome. Although the neurome typically encompasses proteomes of the brain and central nervous system, exciting new roles of these neuropeptidases have been demonstrated in other organ systems. We discuss the involvement of EP24.15 with clinical sequelae involving the use of gonadotropin-releasing hormone (GnRH; LHRH) analogs that act as enzyme inhibitors, in vascular physiology (blood pressure regulation), and in the hematologic system (immune surveillance). Hemodynamic forces, such as cyclic strain and shear stress, on vascular cells, induce an increase in EP24.15 transcription, suggesting that neuropeptidase-mediated hydrolysis of pressor/depressor peptides is likely regulated by changes in hemodynamic force and blood pressure. Lastly, EP24.15 regulates surface expression of major histocompatibility complex Class I proteins in vivo, suggesting that EP24.15 may play an important role in maintenance of immune privilege in sites of increased endogenous expression. In these extraneural systems, regulation of both neuropeptide and other peptide substrates by neuropeptidases indicates that the influence of these enzymes may be more global than was anticipated previously, and suggests that their attributed role as neuropeptidases underestimates their physiologic actions in the neural system.
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PMID:Novel roles of neuropeptide processing enzymes: EC3.4.24.15 in the neurome. 1459 22

The properties of the various brain membrane peptidases capable of hydrolysing released neuropeptides are reviewed, with particular emphasis on endopeptidase-24.11 and angiotensin converting enzyme. The substrate specificities of both enzymes are defined and their relative contribution to the degradation of tachykinins in vitro are considered. One approach to assessing the physiological roles of identified peptidases involves examining the protective effect of selective peptidase inhibitors on the degradation of peptides released from brain slices. This procedure has been applied to study the release of substance P-like immunoreactivity from slices of rat substantia nigra. Inhibition of endopeptidase-24.11, but not of angiotensin converting enzyme, produces a significant increase in recovery of substance P. The specificity and distribution of endopeptidase-24.11 would therefore not be inconsistent with a role in the physiological inactivation of tachykinins, as well as enkephalins. At peripheral sites, LHRH and atrial natriuretic peptide may be important substrates of the enzyme. The endogenous neuropeptide substrate(s) for striatal angiotensin converting enzyme remain unclear.
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PMID:Neuropeptides and their peptidases: Functional considerations. 2050 Dec 42


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