scholarly journals Characterization of a secretase activity which releases angiotensin-converting enzyme from the membrane

1993 ◽  
Vol 292 (2) ◽  
pp. 597-603 ◽  
Author(s):  
S Y Oppong ◽  
N M Hooper
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Human Kidney ◽  
Soluble Form ◽  
Converting Enzyme ◽  
Ph Optimum ◽  
Secretase Activity ◽  
Sds Page ◽  
Microsomal Membranes ◽  
Membrane Bound ◽  
Triton X

Angiotensin-converting enzyme (ACE; EC 3.4.1.15.1) exists in both membrane-bound and soluble forms. Phase separation in Triton X-114 and a competitive e.l.i.s.a. have been employed to characterize the activity which post-translationally converts the amphipathic, membrane-bound form of ACE in pig kidney microvilli into a hydrophilic, soluble form. This secretase activity was enriched to a similar extent as other microvillar membrane proteins, was tightly membrane-associated, being resistant to extensive washing of the microvillar membranes with 0.5 M NaCl, and displayed a pH optimum of 8.4. The ACE secretase was not affected by inhibitors of serine-, thiol- or aspartic-proteases, nor by reducing agents or alpha 2-macroglobulin. The metal chelators, EDTA and 1,10-phenanthroline, inhibited the secretase activity, with, in the case of EDTA, an inhibitor concentration of 2.5 mM causing 50% inhibition. In contrast, EGTA inhibited the secretase by a maximum of 15% at a concentration of 10 mM. The inhibition of EDTA was reactivated substantially (83%) by Mg2+ ions, and partially (34% and 29%) by Zn2+ and Mn2+ ions respectively. This EDTA-sensitive secretase activity was also present in microsomal membranes prepared from pig lung and testis, and from human lung and placenta, but was absent from human kidney and human and pig intestinal brush-border membranes. The form of ACE released from the microvillar membrane by the secretase co-migrated on SDS/PAGE with ACE purified from pig plasma, thus the action and location of the secretase would be consistent with it possibly having a role in the post-translational proteolytic cleavage of membrane-bound ACE to generate the soluble form found in blood, amniotic fluid, seminal plasma and other body fluids.

scholarly journals Palmitoylation of the three isoforms of human endothelin-converting enzyme-1

1999 ◽  
Vol 340 (3) ◽  
pp. 649-656 ◽  
Author(s):  
Anja SCHWEIZER ◽  
Bernd-Michael LÖFFLER ◽  
Jack ROHRER
Keyword(s):  
Covalent Attachment ◽  
Membrane Domains ◽  
Converting Enzyme ◽  
Wild Type ◽  
Immunofluorescence Analysis ◽  
Sds Page ◽  
Endothelin Converting Enzyme ◽  
Membrane Bound ◽  
Triton X

Endothelin-converting enzyme-1 (ECE-1) is a membrane-bound metalloprotease that catalyses the conversion of inactive big endothelins into active endothelins. Here we have examined whether the three isoforms of human ECE-1 (ECE-1a, ECE-1b and ECE-1c) are modified by the covalent attachment of the fatty acid palmitate and have evaluated a potential functional role of this modification. To do this, wild-type and mutant enzymes were expressed and analysed by metabolic labelling with [3H]palmitate, immunoprecipitation and SDS/PAGE. All three ECE-1 isoforms were found to be palmitoylated via hydroxylamine-sensitive thioester bonds. In addition, the isoforms showed similar levels of acylation. Cys46 in ECE-1a, Cys58 in ECE-1b and Cys42 in ECE-1c were identified as sites of palmitoylation and each of these cysteines accounted for all the palmitoylation that occured in the corresponding isoform. Immunofluorescence analysis demonstrated further that palmitoylated and non-palmitoylated ECE-1 isoforms had the same subcellular localizations. Moreover, complete solubility of the three isoforms in Triton X-100 revealed that palmitoylation does not target ECE-1 to cholesterol and sphingolipid-rich membrane domains or caveolae. The enzymic activities of ECE-1a, ECE-1b and ECE-1c were also not significantly affected by the absence of palmitoylation.

scholarly journals Human recombinant membrane-bound aminopeptidase P: production of a soluble form and characterization using novel, internally quenched fluorescent substrates

2005 ◽  
Vol 385 (2) ◽  
pp. 389-397 ◽  
Author(s):  
Giuseppe MOLINARO ◽  
Adriana K. CARMONA ◽  
Maria A. JULIANO ◽  
Luiz JULIANO ◽  
Elena MALITSKAYA ◽  
...  
Keyword(s):  
Amino Acid ◽  
Angiotensin Converting Enzyme ◽  
Angiotensin Converting Enzyme Inhibitors ◽  
Polyclonal Antiserum ◽  
Soluble Form ◽  
Converting Enzyme ◽  
Converting Enzyme Inhibitors ◽  
Fluorescent Peptide ◽  
Membrane Bound ◽  
Aminopeptidase P

APP (aminopeptidase P) has the unique ability to cleave the N-terminal amino acid residue from peptides exhibiting a proline at P1′. Despite its putative involvement in the processing of bioactive peptides, among them the kinins, little is known about the physiological roles of both human forms of APP. The purpose of the present study is first to engineer and characterize a secreted form of hmAPP (human membrane-bound APP). Our biochemical analysis has shown that the expressed glycosylated protein is fully functional, and exhibits enzymic parameters similar to those described previously for mAPP purified from porcine or bovine lungs or expressed from a porcine clone. This soluble form of hmAPP cross-reacts with a polyclonal antiserum raised against a 469-amino-acid hmAPP fragment produced in Escherichia coli. Secondly, we synthesized three internally quenched fluorescent peptide substrates that exhibit a similar affinity for the enzyme than its natural substrates, the kinins, and a higher affinity compared with the tripeptide Arg-Pro-Pro used until now for the quantification of APP in biological samples. These new substrates represent a helpful analytical tool for rapid and reliable screening of patients susceptible to adverse reactions associated with angiotensin-converting enzyme inhibitors or novel vasopeptidase (mixed angiotensin-converting enzyme/neprilysin) inhibitors.

scholarly journals Identification and properties of a peptidyl dipeptidase in the housefly, Musca domestica, that resembles mammalian angiotensin-converting enzyme

1994 ◽  
Vol 299 (3) ◽  
pp. 651-657 ◽  
Author(s):  
N S Lamango ◽  
R E Isaac
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Musca Domestica ◽  
Gel Filtration ◽  
Converting Enzyme ◽  
Ph Optimum ◽  
Somatic Tissues ◽  
Ic50 Values ◽  
Bivalent Metal Ions ◽  
Membrane Bound ◽  
Dipeptidase Activity

[D-Ala2,Leu5]Enkephalin was readily metabolized by membranes (40,000 g pellet) prepared from heads of the housefly, Musca domestica, with Gly3-Phe4 being the major site of cleavage. This hydrolysis was only partially inhibited (40%) by 10 microM phosphoramidon, an inhibitor of endopeptidase-24.11, but was almost totally abolished in the presence of a mixture of 10 microM phosphoramidon and 10 microM captopril, a potent inhibitor of mammalian angiotensin-converting enzyme (ACE). An assay for ACE employing Bz-Gly-His-Leu as the substrate was used to confirm the presence of an ACE-like peptidyl dipeptidase activity in fly head membranes. The peptidase had a Km of 1.91 mM for Bz-Gly-His-Leu and a pH optimum of 8.2. The activity was inhibited by 100 microM EDTA and was greatly activated by ZnCl2 but not other bivalent metal ions. Captopril, lisinopril, fosinoprilat and enalaprilat, all selective inhibitors of mammalian ACE, were also good inhibitors of the insect enzyme with IC50 values of 400 nM, 130 nM, 16 nM and 290 nM respectively. An M(r) value of around 87,000 was obtained for this enzyme from gel-filtration chromatography, indicating that the insect enzyme is similar in size to mammalian testicular ACE (M(r) = 90,000-110,000) and not the larger form of the enzyme (M(r) = 150,000-180,000) found in mammalian somatic tissues. The fly peptidyl dipeptidase was released from membranes into a soluble fraction by incubating the head membranes at 37 degrees C but not at 0 degree C, suggesting that the insect ACE-like enzyme can be solubilized from cell surfaces through the activity of a membrane-bound enzyme activity. In conclusion, we have shown the existence of a peptidyl dipeptidase in membranes from the heads of M. domestica, which has similar properties to those of mammalian ACE.

scholarly journals Regulated cleavage-secretion of the membrane-bound angiotensin-converting enzyme.

1994 ◽  
Vol 269 (3) ◽  
pp. 2125-2130
Author(s):  
R. Ramchandran ◽  
G.C. Sen ◽  
K. Misono ◽  
I. Sen
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Converting Enzyme ◽  
Membrane Bound

scholarly journals Evidence for the involvement of a 66 kDa membrane protein in the synthesis of sterolglucoside in Saccharomyces cerevisiae.

1995 ◽  
Vol 42 (2) ◽  
pp. 269-274 ◽  
Author(s):  
U Lenart ◽  
J Haplova ◽  
P Magdolen ◽  
V Farkas ◽  
G Palamarczyk
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Mass ◽  
Deae Cellulose ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sds Page ◽  
Nonionic Detergent ◽  
Membrane Bound ◽  
Labeled Probe ◽  
Triton X ◽  
Cellulose Column

The membrane-bound sterolglucoside synthase from the yeast Saccharomyces cerevisiae has been solubilized by nonionic detergent, Nonidet P-40, Triton X-100, and partially purified by DEAE-cellulose column chromatography and ammonium sulfate fractionation. SDS/PAGE of the purified fraction revealed the presence of two protein bands of molecular mass 66 kDa and 54 kDa. In an attempt to identify further the polypeptide chain of sterolglucoside synthase, the partially purified enzyme was treated with [di-125I]-5-[3-(p-azidosalicylamide)]allyl-UDPglucose, a photoactive analogue of UDP glucose, which is a substrate for this enzyme. Upon photolysis the 125I-labeled probe was shown to link covalently to the 66 kDa protein. The photoinsertion was competed out by the presence of unlabeled UDPglucose thus suggesting that this protein contains substrate binding site for UDPglucose. Since photoinsertion of the probe to protein of 66 kDa correlates with the molecular mass of the protein visualized upon enzyme purification we postulate that the 66 kDa protein is involved in sterolglucoside synthesis in yeast.

Soluble neutral maltase–glucoamylase from the small intestine: separation and characterization of components with differing affinity for concanavalin A

1982 ◽  
Vol 60 (11) ◽  
pp. 1007-1013 ◽  
Author(s):  
G. Forstner ◽  
A. Salvatore ◽  
L. Lee ◽  
J. Forstner
Keyword(s):  
Concanavalin A ◽  
Gradient Elution ◽  
Soluble Form ◽  
Rat Intestine ◽  
Ph Optimum ◽  
Molecular Weights ◽  
Neutral Ph ◽  
Membrane Bound ◽  
Sepharose 4B

Intestinal maltase with a neutral pH optimum exists in both a brush border membrane-bound form and a soluble form in suckling rat intestine. Previous experiments in our laboratory have shown that the soluble enzyme contains a component which binds much more tightly to concanavalin A (ConA) than solubilized forms of the membrane enzyme. We studied the origin of this component by subjecting neutral, soluble maltase activity to chromatography on Sepharose 4B at age 13, 18 (preweaning), and 25 (postweaning) days. At 13 days, two maltase peaks were obtained with approximate molecular weights of 400 000 (peak I) and 150 000 (peak II). Peak II was less prominent at 18 days and was absent at 25 days. At 13 days, the majority of peak I consisted of material which was bound between 0.025 and 0.05 M α-methyl mannoside on gradient elution chromatography of ConA-Sepharose. Peak II contained material which eluted between 0.075 and 0.3 M α-methyl mannoside. At 25 days, all of the soluble maltase eluted between 0.025 and 0.04 M α-methyl mannoside. Peak I and peak II maltases had similar pH optima and Km's for maltase. Peak II maltase had a fourfold greater activity toward glycogen than peak I maltase with approximately the same activity for palatinose, turanose, and trehalose. Both maltases were precipitated by an antibody raised against adult membrane-bound maltase. Soluble maltase with neutral pH activity in the suckling rat intestine, therefore, consists of two immunologically related isozymes which differ in their molecular weight, their binding by ConA, and their specificity for glycogen. The small isozyme disappears at or about the time of weaning.

scholarly journals Characterization of the soluble, secreted form of urinary meprin

1996 ◽  
Vol 315 (2) ◽  
pp. 461-465 ◽  
Author(s):  
Robert J. BEYNON ◽  
Simon OLIVER ◽  
Duncan H. L. ROBERTSON
Keyword(s):  
Proteolytic Activity ◽  
Protein Band ◽  
Peptide Sequence ◽  
Soluble Form ◽  
Α Subunit ◽  
Alternative Processing ◽  
Sds Page ◽  
Processing Pathways ◽  
Membrane Bound

A soluble form of the kidney membrane metalloendopeptidase, meprin, is present in urine. Urinary meprin is expressed in BALB/C mice with the Mep-1a/a genotype (high meprin, expressing meprin-α and meprin-β) but not in BALB.K mice of the Mep-1b/b genotype (that only express meprin-β). Western blotting with antisera specific to the meprin-α and the meprin-β subunits established that the only form of meprin present in urine samples was derived from meprin-α. This form of meprin is partially active, and comprises at least three variants by non-reducing SDS/PAGE and by zymography and two protein bands on reducing SDS/PAGE. Sequencing of these two bands established that the N-terminus of the larger protein band begins with the pro-peptide sequence of the α-subunit (VSIKH..), whereas the smaller band possessed the mature meprin N-terminal sequence (NAMRDP..). Trypsin is able to remove the pro-peptide, with a concomitant activation in proteolytic activity. After deglycosylation, the size of the pro- and mature forms of urinary meprin are consistent with cleavage in the region of the X–I boundary. There is a pronounced sexual dimorphism in urinary meprin expression. Females secrete a slightly larger form, and its proteolytic activity is about 50% of that released by males. The urinary meprin is therefore a naturally occurring secreted form of this membrane-bound metalloendopeptidase and is more likely to be generated by alternative processing pathways than by specific release mechanisms.

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