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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We discovered an enzyme in human platelets that deamidates substance P and other tachykinins. Because an amidated carboxyl terminus is important for biological activity, we purified and characterized this deamidase. The enzyme, released from human platelets by thrombin, was purified to homogeneity by ammonium sulfate precipitation, followed by chromatography on an octyl-Sepharose column and chromatofocusing on PBE 94. The purified enzyme exhibits esterase, peptidase, and deamidase activities. The peptidase activity (with furylacryloyl-Phe-Phe) is optimal at pH 5.0 while the esterase (benzoyl-tyrosine ethyl ester) and deamidase (D-Ala2-Leu5-enkephalinamide) activities are optimal at pH 7.0. With biologically important peptides, the enzyme acts both as a deamidase (substance P, neurokinin A, and eledoisin) and a carboxy-peptidase (with bradykinin, angiotensin I, substance P-free acid, oxytocin-free acid) at neutrality, although the carboxypeptidase action is faster at pH 5.5. Enkephalins, released upon deamidation of enkephalinamides, were not cleaved. Gly9-NH2 of oxytocin was released without deamidation. Peptides with a penultimate Arg residue were not hydrolyzed. Some properties of the deamidase are similar to those reported for cathepsin A. The deamidase is inhibited by diisopropylfluorophosphate, inhibitors of chymotrypsin-type enzymes, and mercury compounds while other inhibitors of catheptic enzymes, trypsin-like enzymes, and metalloproteases were ineffective. In gel filtration, the native enzyme has an Mr = 94,000 while in non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis the Mr = 52,000 indicating it exists as a dimer. After reduction, deamidase dissociates into two chains of Mr = 33,000 and 21,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. [3H]diisopropylfluorophosphate labeled the active site serine in the Mr = 33,000 chain. The first 25 amino acids of both chains were sequenced. They are identical with the sequences of the two chains of lysosomal "protective protein" which, in turn, has sequence similarity to the KEX1 gene product and carboxypeptidase Y of yeast. This protective protein complexes with beta-galactosidase and neuraminidase in lysosomes and is vitally important in maintaining their activity and stability. A defect in this protein is the cause of galactosialidosis, a severe genetic disorder. The ability of physiological stimuli (e.g. thrombin or collagen) to release the deamidase from platelets indicates that it may also be involved in the local metabolism of bioactive peptides.
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PMID:A peptidase in human platelets that deamidates tachykinins. Probable identity with the lysosomal "protective protein". 169 76

We developed a sensitive and specific heterogeneous enzyme immunoassay for measuring angiotensin I (AI) or renin (EC 3.4.99.19) activities. Linking AI under carefully controlled conditions by means of N-succinimidyl-3-(2-pyridyldithio)propionate to highly purified beta-D-galactosidase (EC 3.2.1.23) produced a well-defined conjugate in high yield. The procedure is simple and consists of three steps: (a) incubate 0.5 mL of plasma with 100 microL of inhibitor solution for 1 h to generate renin activity; (b) incubate this with labeled AI for 1 h at 37 degrees C; and (c) do a double-antibody precipitation. Bound beta-D-galactosidase activity is determined, with O-nitrophenyl-beta-D-galactoside as substrate, by measuring the liberated O-nitrophenol at 410-420 nm. The analytical range of the assay extends from 62.5 to 4000 ng/L, and renin activities so measured in plasma correlate well with those measured by an established radioimmunoassay (n = 35, r = 0.97, intercept -0.6, and slope 1.44).
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PMID:Enzyme immunoassay of angiotensin I and renin. 311 31

To localize angiotensin II type 1a (AT-1a) receptor and to reveal the physiological roles of angiotensin II in the renal microcirculation, we investigated the AT-1a gene deficient mice, generated by a targeted replacement of the AT-1a receptor loci by the lacZ gene (Sugaya et al, J Biol Chem 270: 18719, 1995). Immunohistochemical localization of beta-galactosidase was performed in the heterozygous mutant mice to reveal the expression sites of AT-1a. The AT-1a receptor (that is, beta-galactosidase) was expressed both in the afferent and efferent arteriolar smooth muscles and also in the mesangial cells. The effect of angiotensin II on glomerular arterioles was directly observed using the hydronephrotic mice. Angiotensin II similarly constricted both the afferent and efferent arterioles in the wild-type and heterozygous mutant mice in a dose-dependent manner. This constriction was completely abolished by an AT-1 antagonist, CV-11974. In the homozygous null mutant mice, however, angiotensin II did not affect the arterioles at all. Electron microscopic studies revealed that the mesangial cells made contact with the glomerular basement membrane (GBM) at the capillary neck and also with each other in the wild-type mice. However, in the homozygous null mutant mice, the mesangial cells lost the contact either with GBM or with each other and thus the capillary neck became remarkably wider. The mesangial matrix area appeared loose and enlarged, suggesting impaired mesangial matrix formation. In conclusion, via the AT-1a receptor, angiotensin II equally constricts both the afferent and efferent arterioles and plays an essential role in maintaining the normal glomerular function and structure.
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PMID:Location and action of angiotensin II type 1 receptor in the renal microcirculation. 940 59

Adrenal zona glomerulosa (ZG) cells do not contain nitric oxide (NO) synthase (NOS). We conferred endothelial NOS activity onto adrenal ZG cells through transduction with a recombinant adenovirus encoding the endothelial NOS gene (AdeNOS) to determine the effect of endogenous NO on aldosterone synthesis. A 135-kDa protein band immunoreactive to anti-endothelial NOS antibody was observed in Western blots of AdeNOS-transduced ZG cells but not in control cells or cells transduced with adenovirus encoding the beta-galactosidase gene (AdbetaGal). Nitrate/nitrite production in AdeNOS-transduced ZG cells increased from 0.15+/-0.01 to 0.27+/-0.01 micromol/L after stimulation with 1 nmol/L angiotensin II. The treatment of AdeNOS-transduced cells with 30 micromol/L L-nitro-arginine decreased angiotensin II-stimulated nitrite production from 0.27+/-0. 01 to 0.17+/-0.01 micromol/L. Basal and angiotensin II-stimulated nitrite production was not increased in AdbetaGal-transduced or control cells. AdeNOS-transduced cells demonstrated diaminofluorescein-2 diacetate fluorescence, which was blocked by pretreatment with L-nitro-arginine. Angiotensin II-stimulated aldosterone synthesis decreased from 5123+/-177 pg/mL in AdbetaGal-transduced ZG cells to 72+/-27 pg/mL in AdeNOS-transduced cells. Treatment with the NOS inhibitor thiocitrulline (30 micromol/L) increased angiotensin II-stimulated aldosterone synthesis to 2158+/-45 pg/mL after AdeNOS transduction. These data demonstrate that adenovirus-mediated gene transfer of eNOS in ZG cells results in the expression of active endothelial NOS enzyme and that this endogenous NO production by ZG cells decreases aldosterone synthesis.
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PMID:Inhibition of adrenal cell aldosterone synthesis by endogenous nitric oxide release. 1064 19

Angiotensin II stimulates vascular NADPH oxidase to produce superoxide, which can react with nitric oxide and impair vasomotor function. We tested the hypothesis that the overexpression of endothelial nitric oxide synthase (eNOS) or superoxide dismutase (SOD) would correct angiotensin II-induced endothelial dysfunction. We examined the effects of the gene transfer of eNOS or 2 isoforms of SOD to the aorta in angiotensin II-treated rabbits on vasomotor function. New Zealand White rabbits were treated for 1 week with angiotensin II (100 ng. kg(-1). min(-1)) or saline by osmotic minipumps. In angiotensin II-treated rabbits, mean blood pressure was 107+/-8 mm Hg; it was 67+/-5 mm Hg in saline-infused rabbits (P<0.05). In aortas from angiotensin II-treated rabbits, lucigenin-enhanced chemiluminescence demonstrated a 2.5-fold increase in superoxide levels, and the oxidative fluorescent probe hydroethidine indicated increased superoxide levels throughout the vascular wall, especially in the endothelium and adventitia. Maximal relaxation to acetylcholine was less in aortas from rabbits treated with angiotensin II (72+/-5% versus 87+/-4% in saline-treated rabbits; P<0.01), but responses to sodium nitroprusside were similar. Segments of the thoracic aorta were incubated in vitro with an adenoviral vector that expressed eNOS, copper zinc SOD (CuZnSOD), extracellular SOD (ECSOD), or beta-galactosidase. beta-Gal treatment with adenovirus containing the gene for eNOS (AdeNOS) but not adenovirus containing the gene for beta-gal (Adbeta-gal) (control virus) restored responses to acetylcholine (82+/-3% after AdeNOS and 67+/-4% after Adbeta-gal). Gene transfer of CuZnSOD or ECSOD did not improve the endothelium-dependent relaxation of the aorta in rabbits that received angiotensin II. Thus, gene transfer of eNOS, but not SOD, effectively restores vasomotor function in angiotensin II-infused rabbits.
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PMID:Gene transfer of endothelial nitric oxide synthase reduces angiotensin II-induced endothelial dysfunction. 1067 3

All components of the renin-angiotensin system are localized in the brain. However, because renin is present in very low concentrations, the mechanism by which angiotensin II is formed in the brain remains unclear. We previously reported the development of 2 transgenic mouse models using sensitive reporters, enhanced green fluorescent protein (eGFP) and beta-galactosidase (beta-Gal), to examine the cellular localization of renin and angiotensinogen in the mouse brain. To determine whether renin and angiotensinogen are coexpressed or present in neighboring cells in the rostral ventrolateral medulla (RVLM) and other cardiovascular control regions of the brain, we produced and examined double-transgenic mice, which express eGFP driven by the renin promoter (REN-1c/eGFP) and beta-gal driven by the human angiotensinogen promoter (hAGT/beta-gal). Using these reporter transgenes as sensitive markers for renin and angiotensinogen expression, we conclude that both proteins are coexpressed in the parabrachial nucleus and central nucleus of the amygdala and are in adjacent cells in the RVLM, reticular formation, bed nucleus of the stria terminalis, subfornical organ, and CA1-3 region. These data suggests that, in these areas, both renin and angiotensinogen are in close proximity providing the potential for the local formation of angiotensin I either intracellularly, when there is colocalization, or in the interstitium, when they are in juxtaposed cells.
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PMID:Adjacent expression of renin and angiotensinogen in the rostral ventrolateral medulla using a dual-reporter transgenic model. 1503 61

The interaction among estrogen, angiotensin II (Ang II), and oxidative stress in endothelial progenitor cells (EPCs) remains unknown. We therefore investigated the potential effect of estrogen on Ang II-induced EPC oxidative stress and senescence in EPCs. EPCs were isolated from peripheral blood and characterized. Both reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting were used to assess gp91phox and angiotensin type 1 receptor (AT1R) expression. Immunofluorescence of nitrotyrosine provided evidence of peroxynitrite formation. Our data indicate that Ang II increased the expression of gp91phox mRNA and protein, and these effects were attenuated by 17beta-estradiol (E2). The exposure of cultured EPCs to Ang II (100 nmol/l) significantly accelerated the rate of senescence compared to that in control cells during 14 days in culture as determined by acidic beta-galactosidase staining, and this effect was significantly inhibited by E2 (p < 0.01). Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity by using a PCR-ELISA-based assay. Ang II significantly diminished telomerase activity, although the effect was significantly reduced by pre-treatment with E2 (p < 0.01). Because we previously demonstrated that both the up-regulation of gp91phox and the acceleration of cellular senescence in Ang II-stimulated EPCs could be abolished by pre-treatment with the AT1R- specific antagonist, valsartan, we also explored the effect of estrogen on AT1R expression. Ang II increased AT1R mRNA and protein expression, and these increases were prevented by E2, suggesting that AT1R may at least partially mediate the inhibitory effect of E2 on Ang II-induced acceleration of senescence in EPCs. In conclusion, estrogen reduces Ang II-induced acceleration of senescence in EPCs partially through down-regulation of AT1R expression.
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PMID:Estrogen reduces angiotensin II-induced acceleration of senescence in endothelial progenitor cells. 1609 71

The ability of endothelial progenitor cells (EPCs) to participate in endothelial repair is impaired by angiotensin II (Ang II) and other atherogenic factors. Therefore, we investigated the effects of Ang II on the differentiation and senescence of EPCs derived from bone marrow (BM-EPCs) in an Ang II-infusion rat model. Wistar rats (n=40) were infused with Ang II or vehicle, either alone or in combination with an Ang II type 1 receptor (AT(1)R) blocker (valsartan). Bone marrow cells were obtained from the tibias and femurs. Rats of the Ang II treatment group had a significantly lower number of differentiated, adherent BM-EPCs than those of the non-treated control group. Addition of valsartan restored the level of attached, differentiated BM-EPCs to the level in the non-treated controls. The number of senescent BM-EPCs, as assessed by acidic beta-galactosidase staining, was significantly greater in the Ang II-alone group than the control group, and addition of valsartan dramatically delayed the senescence of BM-EPCs in the Ang II-alone group. A polymerase chain reaction (PCR)-ELISA-based assay revealed that telomerase activity was significantly lower in BM-EPCs from the Ang II-alone group than in those from the control group, and addition of valsartan significantly augmented this activity. An MTS assay revealed that Ang II treatment significantly decreased the functional activity in BM-EPCs, and this effect was significantly reversed by valsartan. In conclusion, Ang II decreased the differentiation and accelerated the senescence of BM-EPCs via AT(1)R.
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PMID:Endothelial progenitor cell differentiation and senescence in an angiotensin II-infusion rat model. 1694 Jul 8

Vascular endothelial cells have a finite cell lifespan and eventually enter an irreversible growth arrest, cellular senescence. The functional changes associated with cellular senescence are thought to contribute to human aging and age-related cardiovascular disorders, e.g. atherosclerosis. In this study, induction of Angiotensin II (Ang II) promoted a growth arrest with phenotypic characteristics of cell senescence, such as enlarged cell shapes, increased senescence-associated beta-galactosidase (SA-beta-gal) positive staining cell, and depressed cell proliferation. Apoptotic changes were increased in senescent cells, with a small subset of the senescent cells showing aberrant morphology such as pronounced nuclear fragmentation or multiple micronuclei. The results suggest cell apoptosis is possibly an important factor in the process of pathologic and physiologic senescence of endothelial cells as well as vascular aging.
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PMID:Apoptosis is involved in the senescence of endothelial cells induced by angiotensin II. 1795 95

Angiotensin II (Ang II) induces reactive oxygen species (ROS) production by human vascular smooth muscle cells (hVSMCs). ROS have been implicated in the development of both acute stress-induced premature senescence (SIPS) and chronic replicative senescence. Global oxidative DNA damage triggers SIPS and telomere DNA damage accelerates replicative senescence, both mediated via p53. This study tests the hypothesis that DNA is an important target for Ang II-induced ROS leading to senescence via telomere-dependent and independent pathways. DNA damage was quantified using the Comet assay, telomere DNA length by Southern blotting and hVSMC senescence by senescence-associated beta-galactosidase staining. Exposure to Ang II increased DNA damage in hVSMCs within 4 hours. Inhibition by an AT1 receptor antagonist (losartan metabolite: E3174) or catalase, confirmed that Ang II-induced DNA damage was AT1 receptor-mediated, via the induction of ROS. Acute exposure to Ang II resulted in SIPS within 24 hours that was prevented by coincubation with E3174 or catalase. SIPS was associated with increased p53 expression but was not dependent on telomere attrition because overexpression of human telomerase did not prevent Ang II-induced SIPS. Exposure to Ang II over several population doublings accelerated the rate of telomere attrition (by >2-fold) and induced premature replicative senescence of hVSMCs--an effect that was also attenuated by E3174 or catalase. These data demonstrate that Ang II-induced ROS-mediated DNA damage results in accelerated biological aging of hVSMCs via 2 mechanisms: (1) Acute SIPS, which is telomere independent, and (2) accelerated replicative senescence which is associated with accelerated telomere attrition.
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PMID:Angiotensin II-mediated oxidative DNA damage accelerates cellular senescence in cultured human vascular smooth muscle cells via telomere-dependent and independent pathways. 1799 83


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