Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50502 (Hip)
 7,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The new ACE inhibitor trandolapril was administered to normal volunteers at daily doses of 0.5, 2, and 8 mg for 10 days. Twenty-one volunteers, aged 21-30 years, were included in the study. To randomly selected groups of seven subjects, each dose was administered in a single-blind fashion. None of the doses induced a consistent fall in blood pressure. Angiotensin-converting enzyme activity (ACE) was measured in vitro using three different synthetic substrates (i.e., Hip-Gly-Gly, Z-Phe-His-Leu, or angiotensin I). Although the degree of ACE inhibition assessed with the three methods varied widely, all methods clearly indicated dose-dependent ACE inhibition. These in vitro results were confirmed by measuring ACE inhibition in vivo using the ratio of plasma angiotensin II (ANG II) to blood angiotensin I (ANG I). The dose-dependent ACE inhibition was paralleled by a dose-dependent rise in active renin and blood angiotensin I levels, most evident on day 10. In contrast, plasma ANG II levels on day 10 were not different whether the volunteers received 0.5 or 8 mg trandolapril. Thus, whereas increasing doses of this new ACE inhibitor progressively enhanced the blockade of ACE activity, this was not reflected by additional reductions of plasma ANG II levels. The progressive enhancement of ACE inhibition seemed to be offset by the accentuation of the compensatory rise in renin and ANG I, which was still partially converted to ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reactive hyperreninemia is a major determinant of plasma angiotensin II during ACE inhibition. 168 24

Incubation of various authentic peptides with rat CSF in vitro and analysis of their products by HPLC demonstrated the presence in CSF of a peptidyl dipeptidase [peptidyl dipeptide hydrolase; angiotensin I converting enzyme (ACE); kininase II; EC 3.4.15.1] which sequentially degraded bradykinin (BK) by liberating the carboxy-terminal dipeptides and converted angiotensin I to angiotensin II. This CSF enzyme was gel-chromatographed by means of HPLC, and the molecular weight was estimated. The susceptibility to various peptidase inhibitors of the rat CSF enzyme, as well as the effect of NaCl on the degradation of BK and Hip-His-Leu catalyzed by it, was also determined. These properties were compared with those of ACE or kininase II from brain or other tissues, as described in the literature. NaCl was shown to exert specific and concentration-dependent effects on each step of the sequential degradation of BK, via BK(1-7) to BK(1-5), catalyzed by the enzyme. In addition, the enzyme system for metabolism of BK appears to differ between rat CSF and blood, the former containing exclusively kininase II, whereas the latter contains both kininase I (carboxypeptidase N; EC 3.4.12.7) and kininase II.
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PMID:Some characteristics of a peptidyl dipeptidase (kininase II) from rat CSF: differential effects of NaCl on the sequential degradation steps of bradykinin. 217 62

Angiotensin I-converting enzyme (ACE) is present in human amniotic fluid. We characterized the enzyme by both its antigenic and enzymatic properties. Using a specific direct radioimmunoassay, ACE was quantified and characterized in each of the 19 samples tested. Mean level was 136 +/- 83 ng/ml. Amniotic ACE completely crossreacted, like that in plasma and kidney, with antibodies raised against the lung enzyme. ACE activity in amniotic fluid averaged 8.7 +/- 5.6 microU/ml using Hip-His-Leu as substrate and was significantly correlated with ACE antigen levels. ACE was not associated with the cells or the free intracellular organelles in amniotic fluid, and the enzyme was present in soluble form. Angiotensinase activity and high levels of kininase activity were found in amniotic fluid. Inhibition studies with captopril and anti-human ACE antibodies suggest that angiotensinases and kininases other than ACE were also present. Because renin, mostly in inactive form, and angiotensinogen were also found in these amniotic fluids, it appears that a complete, although not fully activated, renin angiotensin system is present in amniotic fluid and fetal membranes during pregnancy.
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PMID:Angiotensin I-converting enzyme in amniotic fluid. 609 99

Angiotensin-converting enzyme was solubilized from bovine lung with detergent and purified over 2300-fold to physical homogeneity by a combination of ammonium sulfate fractionation, molecular sieve chromatography, and ion exchange chromatography. The purified enzyme had an apparent molecular weight of 126,000 in both the denatured, and reduced, denatured forms as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified enzyme had a specific activity of 13.6 units/mg. It was inhibited by EDTA and activated by chloride ion. Chloride functioned as a nonessential activator by raising the Vmax 4.26-fold and lowering the KM 5.99-fold under saturating conditions. Under these conditions, the Vmax was 1.2 mumol/min/unit and the KM was 1.3 mM. Three series of peptides having the general structures, Hip-His-X, Hip-X-Leu, and Hip-X-His-Leu were synthesized and used to examine the binding specificity and substrate specificity of the enzyme for amino acids in the COOH-terminal (P'2), penultimate COOH-terminal (P'1), and antepenultimate COOH terminal (P1) peptide positions. These studies indicated that in terms of binding specificity, the relative importance of these three positions was P'2 > P'1 > P1, while the reverse order P1 > P'1 > P'2 was observed for the relative contribution to substrate specificity. Three peptides, Hip-His-D-Leu, Hip-D-His-Leu, and Hip-D-Phe-His-Leu, were also synthesized and used to examine the stereochemical requirements of the enzyme in terms of both peptide binding and hydrolysis. Hydrolysis was found to require an L amino acid in all three positions. In contrast, all three peptides bound to the enzyme.
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PMID:Purification and substrate specificity of bovine angiotensin-converting enzyme. 625 46

Angiotensin-converting enzyme (ACE) was studied in preparations of microvessels isolated from rabbit cerebral cortex. Activity was determined by measuring the degradation of hippuryl-histidyl-leucine (Hip-His-Leu) by the intact microvessels in a physiological salt solution at pH 7.4. ACE activity was dependent on both substrate and chloride ion concentration and was inhibited by captopril in a manner similar to that observed previously with tissue homogenates. Angiotensin I was rapidly degraded by the intact microvessels, even in the presence of 10(-6)M captopril. An advantage of the methodology employed was the ability to pretreat the microvessels and then assess the effect of pretreatment by transfer to a postincubation assay system. Pretreatment with a hyperosmolar urea solution did not change ACE activity or cause release of ACE from the microvessels, although lactic dehydrogenase and lysosomal enzymes were released. Pretreatment with captopril caused a lag in the subsequent degradation of Hip-His-Leu, presumably reflecting dissociation of inhibitor from the cell-associated enzyme. ACE activity was unaffected by hypoxic or anoxic incubation conditions. The ability to measure ACE activity of the microvessels in vitro provides a unique opportunity to study the properties of the enzyme in intact cerebrovascular endothelial cells.
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PMID:Properties of angiotensin-converting enzyme in intact cerebral microvessels. 626 Jun 46

Kininase activity, which inactivates kinins, was measured in seven regions of the rat brain (i.e., the cerebral cortex, cerebellum, striatum, midbrain, hippocampus, hypothalamus, medulla oblongata), and in the spinal cord with a bioassay method using bradykinin as the substrate. Specific kininase activities in the cerebellum and striatum were higher than those in the other five regions or the spinal cord. Angiotensin-converting enzyme activity, which was measured fluorometrically using Hip-His-Leu as substrate, showed high activity in the striatum and cerebellum. These findings suggest that the presence of high concentrations of peptidases plays a role in the degradation of kinins and/or other peptides in these areas.
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PMID:Regional distribution of kininase in rat brain. 626 46

Angiotensin-converting enzyme (ACE) in rat brain closely resembled that in lung in its kinetics with the substrate Hip-His Leu, the inhibitors SQ 20,881 and SQ 14,225, and iun its Cl- activation profile. Modification of dietary NaCl intake was associated with marked changes in brain ACE activity. Sodium-loaded rats had lower activity of ACE in hypothalamus, striatum, and midbrain, and higher activity in spinal cord compared to controls. In sodium-restricted rats, ACE was elevated in pituitary and depressed in spinal cord. Chronic intravenous infusion of angiotensin (AII) was associated with a pattern of changes partly resembling sodium loading: ACE was depressed in hypothalamus and striatum but elevated in midbrain. After chronic intracerebroventricular infusion of AII, ACE was elevated in striatum and hippocampus, and depressed in spinal cord; a pattern of changes quite different from those associated with intravenous AII. These results show that ACE in several brain regions is sensitive to dietary sodium intake and support the hypothesis that angiotensin-containing neurons in these areas might be responsive to NaCl status of the animal. The observed changes in brain ACE do not seem to be explained in any simple manner by changes in circulating or central angiotensin II.
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PMID:Modulation of brain angiotensin-converting enzyme by dietary sodium and chronic intravenous and intracerebroventricular fusion of angiotensin II. 628 77

Angiotensin I-converting enzyme (ACE, E.C.3.4.15.1) has been recently shown to contain two very similar domains, each of which bears a functional active site hydrolyzing Hip-His-Leu or angiotensin I (AI). The substrate specificity of the two active sites of ACE was compared using wild-type recombinant ACE and mutants, where one active site is suppressed by deletion or inactivated by mutations of 2 histidines coordinating an essential zinc atom. Both active sites converted bradykinin (BK) to BK1-7 and BK1-5 with similar kinetics and with Kappm at least 30 times lower and kcat/kappm 10 times higher than for AI. The carboxyl-terminal active site, but not the amino-terminal site, was activated by chloride; however, chloride activation was minimal compared with AI. Both domains also hydrolyzed substance P and cleaved a carboxyl-terminal protected dipeptide and tripeptide. The carboxyl-terminal active site was more readily activated by chloride and hydrolyzed substance P faster. Luteinizing-hormone releasing hormone was hydrolyzed by both active sites, but hydrolysis by the amino-terminal active site was faster. It performed the endoproteolytic amino-terminal cleavage of this peptide at least 30 times faster than the carboxyl-terminal active site. Both active sites cleaved a carboxyl-terminal tripeptide from luteinizing hormone-releasing hormone. Thus, both active sites of ACE possess dipeptidyl carboxypeptidase and endopeptidase activities. However, only the carboxyl-terminal active site can undergo a chloride-induced alteration that greatly enhances the hydrolysis of AI or substance P, and the amino-terminal active site possesses an unusual amino-terminal endoproteolytic specificity for a natural peptide. This suggests physiologically important differences between the subsites of the two active centers, and different substrate specificity, despite the high degree of sequence homology.
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PMID:Differences in the properties and enzymatic specificities of the two active sites of angiotensin I-converting enzyme (kininase II). Studies with bradykinin and other natural peptides. 768 54

1. Plasma dipeptidyl carboxypeptidase-1 (DCP1; angiotensin I-converting enzyme, kininase II; EC 3.4.15.1) tracks with the deletion allele in genotypes of a 287 bp insertion/deletion (I/D) polymorphism of its gene, DCP1, in healthy Caucasian populations. The aim of the present study was to see whether genotype has a similar influence on plasma DCP1 in hypertensives. 2. The study involved 35 Caucasian patients with severe, familial essential hypertension, who were not being treated with DCP1 inhibitors, and 94 normotensives. Genotyping for the I/D polymorphism was performed by polymerase chain reaction and plasma DCP1 activity was measured by rate of hydrolysis of both [3H]-Hip-Gly-Gly and Hip-His-Leu. 3. Plasma DCP1 activity (nmol Gly-Gly/min per mL; mean +/- s.e.m.) was 67 +/- 2, 82 +/- 4 and 91 +/- 6 in II, ID and DD hypertensives, respectively, which was similar to values of 68 +/- 4, 82 +/- 3 and 94 +/- 3 in normotensives (P = 0.0001 by one-way analysis of variance). Results for the His-Leu assay indicated similar tracking with genotype. 4. The Michaelis constant (mumol Hip-Gly-Gly/mL; mean +/- s.e.m., n = 10) for DD subjects was the same as for II subjects (10.6 +/- 1.6 vs 11.1 +/- 2.3; P = 0.86). 5. In conclusion, in severely hypertensive Caucasian subjects, plasma DCP1 activity is subject to a similar genotypic influence in hypertensives as has been reported previously in normotensives. Furthermore, the plasma DCP1 enzyme itself appears to be functionally similar for each genotype.
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PMID:Genotypic influence on plasma dipeptidyl carboxypeptidase-1 activity in hypertensives. 792 4

Angiotensin I-converting enzyme (ACE) is composed of two highly similar domains called the N and C domains, which display some contrasting enzymatic properties. We constructed two ACE chimeras: chimera 1, comprised of the N domain containing the central 60 amino acid residues of the C domain, and chimera 2, comprised of the C domain containing the central 60 amino acid residues of the N domain. Chimeras 1 and 2 displayed Km values for Hip-His-Leu and Z-Phe-His-Leu and kcat ratios for these two substrates similar to that of the N and C domains, respectively. Thus, the short sequence exchanged between the two domains does not confer the specific properties of that domain for these two substrates but, rather, such specific properties must arise from the sequences surrounding the central region in each domain.
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PMID:A study of chimeras constructed with the two domains of angiotensin I-converting enzyme. 853 62


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