Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.15.1 (ACE)
 18,300 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was initiated to explore the possibility that an increase in the supply of gluconeogenic precursors contributes to the overproduction of glucose by the liver in NIDDM patients. To address this issue, a form of experimental NIDDM was produced in rats by injecting a low dose (38 mg/kg) of STZ and comparing lactate and alanine production and PDH activity in skeletal muscle and isolated adipocytes from normal and diabetic rats. Skeletal muscle lactate production was measured by using a hindlimb perfusion technique and was significantly greater (P < 0.01) in the diabetic rats compared with two groups of control rats: one perfused at normal glucose levels and the other perfused at glucose concentrations comparable with those observed in diabetic rats. Alanine production by hindlimb from diabetic rats was 46% greater than hindlimbs from control rats perfused at normal glucose levels (P < 0.01) but was not significantly greater than control rats perfused at diabetic glucose levels. The percentage of glucose converted to lactate by muscle from both control groups was 4-5%, significantly lower than the 18% conversion rate observed in diabetic animals (P < 0.001). An increase in the ratio of lactate produced/glucose transport by isolated adipocytes from diabetic rats also was observed when measured in both the basal state (0.65 +/- 0.12 vs. 0.15 +/- 0.03, P < 0.01) and in the presence of maximal amounts of insulin (0.15 +/- 0.02 vs. 0.04 +/- 0.01, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Lactate production and pyruvate dehydrogenase activity in fat and skeletal muscle from diabetic rats. 144 95

The parameter Amax/Km (product of reactant enzyme mass in perfused microvessels and the constant kcat/Km), calculated from in vivo assays of pulmonary endothelial ectoenzymes (e.g., angiotensin-converting enzyme, ACE), can provide estimates of the perfused pulmonary microvascular surface area (PMSA) in the absence of enzyme dysfunction. We examined the relationship between PMSA and pulmonary blood flow (Qb) in anesthetized rabbits placed on total heart bypass, using [3H]benzoyl-Phe-Ala-Pro (BPAP) as the ACE substrate. When Qb was increased from 250 to 1,100 ml/min, at zone 3 conditions, pulmonary arterial pressure increased, pulmonary vascular resistance (PVR) decreased, and Amax/Km increased linearly, reflecting increasing PMSA. When only the left lung was perfused, increasing Qb from 250 to 636 +/- 17 ml/min (the last value representing fully recruited and/or distended vascular bed), PVR decreased, while Amax/Km increased. When Qb was further increased to 791 +/- 44 ml/min, both PVR and Amax/Km remained unchanged, confirming the lack of additional changes in PMSA. We conclude that Amax/Km provides a sensitive indication of PMSA, because it 1) increases with increasing Qb and decreasing PVR, 2) reaches a maximum at Qb values that correspond to the minimal values in PVR, and 3) like PVR, did not change with further increases in Qb. Compared with predicted changes in PMSA produced by either microvascular recruitment alone or distension alone, our data indicate that recruitment is a larger contributor to the observed increase in PMSA.
 ...
PMID:Effects of blood flow on lung ACE kinetics: evidence for microvascular recruitment. 166 34

Pulmonary endothelial aminopeptidase P (AmP) may be an important contributor to the inactivation of circulating bradykinin in certain species. To examine this possibility, we measured AMP activity in vivo and in vitro using Arg-Pro-Pro-[3H]benzylamide (3H-APPB) as substrate under conditions of first order enzyme kinetics. Utilizing multiple indicator dilution techniques, metabolism of 3H-APPB to Arg and Pro-Pro-[3H]benzylamide by AmP was not detectable during a single transpulmonary passage in anesthetized rabbits (n = 4), cats (n = 3) and pigs (n = 4). However, percent metabolism of 3H-APPB ranged from 54 to 63% in anesthetized rats (n = 6). In all experiments, the substrate remained within the vascular space and was thus accessible to endothelial and blood AmP only. At the same time, single-pass transpulmonary percent metabolism of [14C]benzoyl-Ala-Gly-Pro by endothelial-bound angiotensin converting enzyme was remarkably similar among rabbits, cats, rats and pigs (60-65%). In culture, Vmax/Km of AmP was 3 to 10 x 10(-4) min-1 for human basal arterial and rabbit and bovine pulmonary arterial endothelial cell monolayers (2 x 10(5) cells). AmP activity in the supernatant of lung and kidney tissue (homogenized in saline containing 1-o-n-octyl-beta-glucopyranoside) from rabbit, cat, pig and rat expressed as Vmax/Km(min-1) per (g wet tissue/ml) was 0.74, 2.25, 3.91 and 185.8 (lung), and 1.0, 3.7, 8.4 and 438.3 (kidney), respectively. Similarly, Vmax/Km values of AmP in plasmas of cat, dog, rabbit, pig, calf (serum), human and rat were 0, 0.016, 0.025, 0.068, 0.191, 0.237 and 3.53 min-1. These results suggest that 1) there are large interspecies variations in AmP activities of plasma, lung and kidney; 2) of the species studied, the rat contains the largest activities of AmP; and 3) AmP appears to be located on the luminal surface of the rat pulmonary endothelium.
 ...
PMID:Species variation in pulmonary endothelial aminopeptidase P activity. 176 77

Neurotensin (NT) endopeptidase (EC 3.4.24.16) has been purified about 800-fold from pig brain by four sequential chromatographic steps depending on ion-exchange and hydrophobic interactions. Two types of preparation were studied: one from a Triton X-100-solubilized membrane fraction, and the other from the soluble fraction containing 90% or more of the total activity in the homogenate. NT endopeptidase activity was monitored by high-precision liquid chromatography of the two peptide products, characterized as NT-(1-10) and NT-(1-8), resulting from cleavage of the Pro10-Tyr11 and Arg8-Arg9 bonds respectively. As purification proceeded, from both membranes and cytosol, the yield of the two products achieved a constant ratio of 5:1 and this ratio was reproduced in repeated purifications. However, a distinct peptidase which hydrolysed exclusively at the Arg8-Arg9 bond was partially resolved from NT endopeptidase by chromatography on hydroxyapatite, and this activity was further purified and assigned to endopeptidase-24.15 (EC 3.4.24.15). SDS/PAGE of both preparations of neurotensin endopeptidase revealed a major band of apparent Mr 75000, and treatment of the membrane-associated form with N-Glycanase gave no evidence that the enzyme was a glycoprotein. The membrane-associated and cytosol forms of NT endopeptidase activities, monitored for both NT-(1-10) and NT-(1-8) products, were compared in their responses to 1,10-phenanthroline, EDTA, dithiothreitol (DTT) and some synthetic site-directed inhibitors of endopeptidase-24.15 or peptidyl dipeptidase A. The effects revealed no significant differences between the two preparations, nor did the reagents discriminate between the activities generating the two NT fragments. The partially purified form of endopeptidase-24.15 was also included in this comparison: while some responses were similar, this peptidase was distinguishable in its activation by DTT and its relative resistance to inhibition by EDTA. Both forms of NT endopeptidase were found to hydrolyse other substrates, including Boc-Phe-Ala-Ala-Phe-4-aminobenzoate, bradykinin and substance P (these at faster rates than neurotensin), as well as dynorphin A-(1-8) and luliberin. The bonds hydrolysed in these neuropeptides, as well as in angiotensins I and II and alpha-neoendorphin, were defined. These studies confirm that NT endopeptidase is distinct from endopeptidase-24.15. They further show that the former is a soluble enzyme, not an integral membrane protein, that it is not peptide-specific and that it might be more appropriately named. enzyme, not an integral membrane protein, that it is not peptide-specific and
 ...
PMID:Purification and properties of a neurotensin-degrading endopeptidase from pig brain. 190 21

Conversion of the octapeptide dynorphin (Dyn) A-(1-8) to Leu5-enkephalin (LE) by endopeptidase EC 3.4.24.15 (EP-24.15) in vivo was examined using the technique of ventriculocisternal perfusion. Peptides were administered intracerebroventricularly in the presence or absence of the EP-24.15 inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Phe-p-aminobenzoate (cFPAAF-pAB) via cannulae placed into the lateral ventricle of urethane-anesthetized rats. The concentration of Dyn-like peptides and LE within the CSF was monitored by radioimmunoassay in samples of CSF taken from a second cannula placed in the cisterna magna. In the absence of inhibitor, less than 5% of the Dyn A-(1-8) administered was recovered in CSF. Immunoreactive LE, which is normally not found in CSF, increased rapidly in content following Dyn A-(1-8) infusion, an observation suggesting that the larger peptide is converted to LE. When the inhibitor cFPAAF-pAB was coadministered with Dyn A-(1-8), the concentration of immunoreactive Dyn A-(1-8) after 5 min was 40 times higher than that found in the absence of inhibitor. The angiotensin converting enzyme inhibitor captopril reduced the degradation of Dyn A-(1-8) to a much lesser degree. The inhibitor of EP-24.15 also afforded some protection of other Dyn-like peptides. No EP-24.15 activity was found in rat CSF, whereas high activity was found in the choroid plexus. Taken together, these data clearly indicate that an ectoenzyme form of EP-24.15 rapidly converts intracerebroventricularly administered Dyn-like peptides to LE.
 ...
PMID:An inhibitor of endopeptidase-24.15 blocks the degradation of intraventricularly administered dynorphins. 197 55

A versatile method for localized (1H) NMR spectroscopy is presented. The method intrinsically combines B0-based spatial localization with the possibility of water suppression and spectral editing. With this sequence it is feasible to localize not only single spectra but also phase-encoded images and spectroscopic images. The technique essentially integrates the "Hahn spin-echo" with the "stimulated echo" sequence and is therefore called ACE (acquiring combined echoes). It realizes water-suppressed three-dimensional localization in a single shot and can be used for localized shimming. Studies in which the new method is applied to phantoms with metabolites diluted at low concentrations are presented. Discrimination between lactate and alanine, employing an adapted spectral editing method with complete inversion, combined with simultaneous water suppression and localization of a 0.06-cc volume is shown. The suppression of signals from outside the selected volume is greater than or equal to 24,000. Also, the method is demonstrated by in vivo experiments at 6.3 T. Localized water-suppressed 1H spectra are obtained completely noninvasively, leaving scalp and fur intact, from well-defined volumes of 0.15 cc in the brain of a living rat. Water-suppressed spectroscopic imaging over a localized volume with "body" coil excitation and noninvasive surface coil detection yielded spectra from voxels as small as 25 microliters in the in vivo rat brain.
 ...
PMID:ACE: a single-shot method for water-suppressed localization and editing of spectra, images, and spectroscopic images. 204 28

The angiotensin I-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) inhibitor, ramiprilat (2-[N-[(S)-1-ethoxycarbonyl-3-phenylpropyl]-L-Ala]-(1S,3S,5S)-2- azabicyclo[3.3.0]octane-3-carboxylic acid), is shown to exist in tow conformational isomers, cis and trans, which interconvert around the amide bond. The two conformers were separated by reversed-phase high-performance liquid chromatography. The conformers were identified by nuclear Overhauser effect measurements. From line shape analysis the isomerization rate constants were determined to be kcis----trans = 15 s-1 and ktrans----cis = 5 s-1 at 368 K in [2H]phosphate buffer (p2H 7.5). By enzyme kinetic studies using 3-(2-furylacryloyl)-L-Phe-Gly-Gly as substrate, the trans conformer was found to be the most potent enzyme inhibitor, whereas the cis conformer had a very low inhibitory effect. A new inhibition mechanism is presented for this type of slow, tight-binding inhibitors that contain an amide bond. This mechanism involves an equilibrium between the two conformers and the enzyme-bound inhibitor complex.
 ...
PMID:Cis-trans isomerization of an angiotensin I-converting enzyme inhibitor. An enzyme kinetic and nuclear magnetic resonance study. 217 61

1. We determined apparent Ki constants of two inhibitors, captopril and CL242,817, for pulmonary endothelial-bound angiotensin converting enzyme (ACE) in anaesthetized rabbits. [3H]-benzoyl-Phe-Ala-Pro was used as the substrate. The apparent kinetic parameters Km and Amax (product of Vmax and microvascular plasma volume) were measured, as was the ratio (Amax/Km) (measured under first order reaction conditions) before and 30s after the i.v. administration of captopril 10 nmol kg-1 or CL242,817, 35 nmol kg-1. 2. Under mixed order reaction conditions, ([S] greater than or equal to Km), apparent Km values increased from 12.2 +/- 1.9 microM to 32.9 +/- 3.3 microM (P less than 0.05) in the captopril-treated rabbits and from 9.3 +/- 2.3 microM to 45.8 +/- 9.8 microM (P less than 0.05) in the CL242,817-treated rabbits, indicative of competitive inhibition. However, apparent Amax values decreased from 10.3 +/- 2.1 to 4.5 +/- 0.8 mumol min-1 (P less than 0.05) and 8.9 +/- 1.7 to 4.8 +/- 0.5 mumol min-1 (P less than 0.05), respectively. 3. Under first order reaction conditions ([S] much less than Km), the Amax/Km ratio decreased from 763 +/- 100 to 125 +/- 38 ml min-1 (P less than 0.05) and 1009 +/- 149 to 126 +/- 44 ml min-1 (P less than 0.05) in the captopril- and CL242,817-treated groups respectively. 4. When the single pass transpulmonary binding of 80pmol [3H]-RAC-X-65 (an ACE inhibitor) was measured in additional rabbits, a significant (P < 0.05) decrease in RAC-X-65 binding was observed 30s after captopril (80% decrease) or CL242,817 (85% decrease), a result expected for a loss of catalytically active enzyme mass due to tightly bound captopril or CL242,817. 5. These results indicate that, in vivo, both captopril and CL242,817 are competitive, tight binding inhibitors of lung ACE. Furthermore, they suggest means for evaluating the interaction of other potential ACE inhibitors with the pulmonary endothelial membrane-bound enzyme, in vivo, possibly in phase I clinical trials.
 ...
PMID:Inhibition of endothelial-bound angiotensin converting enzyme, in vivo. 228 54

We have determined kinetic characteristics of angiotensin converting enzyme, 5'-nucleotidase and transmembrane serotonin uptake and metabolism in cultured calf pulmonary arterial endothelial cells. Angiotensin converting enzyme activity was 2.8 +/- 0.03 Units/10(6) cells (N = 19; 1 Unit: amount of enzyme required to metabolize 1% of substrate, benzoyl-Phe-Ala-Pro, in 1 min under conditions of first order reaction kinetics) in confluent monolayers and 2.31 +/- 0.06 Units/10(6) cells (N = 20) in homogenates. 5'-Nucleotidase activity (substrate: 5'-AMP) was 0.25 +/- 0.01 Units/10(6) cells (N = 19) in monolayers and 0.26 +/- 0.01 Units/10(6) cells (N = 20) in homogenates. Kinetic constants for angiotensin converting enzyme were: Km = 7.6 microM, Vmax = 5.2 nmol/hour/10(6) cells and for 5'-nucleotidase: Km = 52.6 microM, Vmax = 6.3 nmol/hour/10(6) cells. These data confirm that both angiotensin converting enzyme and 5'-nucleotidase are ectoenzymes with no cytoplasmic activity. Serotonin uptake exhibited both a saturable (Km = 0.27 microM, Vmax = 17 pmol/hour/10(6) cells) and a non-saturable component.
 ...
PMID:Plasmalemmal metabolic activities in cultured calf pulmonary arterial endothelial cells. 241 94

Angiotensin converting enzyme activity was measured in intact aortic rings utilizing the synthetic tripeptide [3H]-benzoyl-Phe-Ala-Pro as the substrate. Intact aortic rings possessed angiotensin converting enzyme activity which was blocked by captopril. Enzyme activity was reduced by approximately 30% after removal of the endothelium by chemical or mechanical methods. The remaining activity was also captopril-sensitive. These results suggest that in addition to endothelium, angiotensin converting enzyme activity is present in other vascular cells and may contribute to the metabolism of angiotensin I generated within the vessel wall.
 ...
PMID:Angiotensin converting enzyme activity is present in the endothelium-denuded aorta. 255 7


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>