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PubMed1996

Evaluation of protein and peptide hydrolases in DOCA-salt hypertensive rat treated with chlorthalidone.

We have reported that chlorthalidone (Chlor) prevents the development of heart hypertrophy in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The present study was carried out to determine whether Chlor (8 mg/day per animal, added to the food, for 20 days) affects kidney and heart hypertrophy in DOCA-salt (8 mg/kg, sc, twice a week) rats by causing alterations in protein and peptide hydrolysis. Heart (left ventricle) and kidney enzyme activities were measured in tissue homogenates from normal-control, salt-control, DOCA-salt and DOCA-salt-Chlor male Wistar rats (N = 6 for each group), using azocasein as the substrate for proteolytic enzymes and specific peptides for prolylendopeptidase (PEP) and multicatalytic proteinase (MCP). The tissue weight/body weight ratio increased in parallel to elevation of blood pressure. The left ventricular muscle hypertrophy (26%, P < 0.05) present in the DOCA-salt hypertensive group was completely prevented by simultaneous Chlor treatment. Chlor treatment did not change the kidney hypertrophy (+79%, P < 0.;05) observed in the salt-control (+57%, P < 0.05) and DOCA-salt (+74%, P < 0.05) groups. The hydrolysis of peptides by PEP and MCP was similar in the normal and salt-control groups. The heart PEP activity was 24% higher (P < 0.01) in DOCA-salt rats, whereas MCP activity was not different when compared to control groups. DOCA-salt treatment increased MCP activity in the kidney by 44% while PEP activity did not differ from that of control groups. The hydrolysis of proteins by heart enzymes was increased by salt by 47%. Chlor treatment restored the reduction in protein hydrolysis induced by DOCA-salt (a 21% decrease, P < 0.05) to a level similar to that of the normal-control group. Similarly, Chlor coadministration prevented the 30% reduction in renal proteolytic activity elicited by DOCA-salt treatment. Although Chlor treatment prevented the DOCA-salt-induced reduction in protein hydrolysis, this response did not interfere with kidney hypertrophy. The mechanism by which hypertension produces hypertrophy is unclear, but our results suggest that this structural modification is not related to the activities of some peptidases, e.g. protein and peptide hydrolases.

Animals↗
PubMed1979

[Spontaneous solubilization of mcuosal peptide hydrolases in rat small intestine].

In vitro incubations of small intestine preparation lead to the spontaneous release of mucosal enzymes into the incubation medium, due to superficial dissolution and membrane lesions. One-hour anaerobic incubation of everted small intestine segments produces the liberation of from 13% (leucine arylamidase) to 30% (Gly-L-Pro-splitting peptide hydrolase) of the mucosal enzyme activities. Under the conditions of in vivo perfusion, the solubilization rates are from 50 to 80% lower than these values. The tendency to solubilization is only in part reduced to a significant extent by the saturation of the incubation medium with oxygen, but it does not reach the in vivo level. The detectability of membrane-bound and intracellular marker enzymes in the incubation medium permits no conclusions concerning the physiological localization of the released peptidases.

Anaerobiosis↗
PubMed1990

Signal peptidases and signal peptide hydrolases.

Signal peptidases, the endoproteases that remove the amino-terminal signal sequence from many secretory proteins, have been isolated from various sources. Seven signal peptidases have been purified, two from E. coli, two from mammalian sources, and three from mitochondrial matrix. The mitochondrial enzymes are soluble and function as a heterogeneous dimer. The mammalian enzymes are isolated as a complex and share a common glycosylated subunit. The bacterial enzymes are isolated as monomers and show no sequence homology with each other or the mammalian enzymes. The membrane-bound enzymes seem to require a substrate containing a consensus sequence following the -3, -1 rule of von Heijne at the cleavage site; however, processing of the substrate is strongly influenced by the hydrophobic region of the signal peptide. The enzymes appear to recognize an unknown three-dimensional motif rather than a specific amino acid sequence around the cleavage site. The matrix mitochondrial enzymes are metallo-endopeptidases; however, the other signal peptidases may belong to a unique class of proteases as they are resistant to chelators and most protease inhibitors. There are no data concerning the substrate binding site of these enzymes. In vivo, the signal peptide is rapidly degraded. Three different enzymes in Escherichia coli that can degrade a signal peptide in vitro have been identified. The intact signal peptide is not accumulated in mutants lacking these enzymes, which suggests that these peptidases individually are not responsible for the degradation of an intact signal peptide in vivo. It is speculated that signal peptidases and signal peptide hydrolases are integral components of the secretory pathway and that inhibition of the terminal steps can block translocation.

Animals↗
PubMed1983

Peptide hydrolase activities in seedlings and hormone-treated cotyledons of pumpkin (Cucurbita pepo).

Enzymes hydrolyzing Gly-Ala-, Met-Met- and Pro-4-phenylazo-phenylamides, and N-benzoyl-L-arginine-4-nitroanilide have been identified in germinating seeds and cotyledons of pumpkin (Cucurbita pepo). The enzyme activities per cotyledon increase markedly during the germination process, but the proportion of enhancement depends on the type of enzyme species. The increase in enzyme activities is due to de novo synthesis as shown by cycloheximide treatment and is influenced by phytohormones (cytokinins and abscissic acid). In isolated cotyledons exogenous cytokinin (benzyladenine) obviously can replace the effect of the embryo as the source of endogenous hormone. Abscissic acid counteracts the cytokinin effect. It is suggested that aminopeptidases have a biological function in reserve protein degradation of the cotyledons during seed germination. Our results do not support the assumption that the embryonic axis of the growing seedling serves as a "sink" of proteolytic products resulting in an activation of peptide hydrolases in the cotyledons, but rather de novo synthesis of these enzymes seems to be controlled by substances (phytohormones) originating from the embryo.

Aminopeptidases↗
PubMed1982

Intracellular Localization of Peptide Hydrolases in Wheat (Triticum aestivum L.) Leaves.

Protoplasts from 8- to 9-day-old wheat (Triticum aestivum L.) leaves were used to isolate organelles which were examined for their contents of peptide hydrolase enzymes and, in the case of vacuoles, other acid hydrolases. High yields of intact chloroplasts were obtained using both equilibrium density gradient centrifugation and velocity sedimentation centrifugation on sucrose-sorbitol gradients. Aminopeptidase activity was found to be distributed, in approximately equal proportions, between the chloroplasts and cytoplasm. Leucyltyrosine dipeptidase was mainly found in the cytoplasm, although about 27% was associated with the chloroplasts. Vacuoles shown to be free from Cellulysin contamination contained all of the protoplast carboxypeptidase and hemoglobin-degrading activities. The acid hydrolases, phosphodiesterase, acid phosphatase, alpha-mannosidase, and beta-N-acetylglucosamidase were found in the vacuole to varying degrees, but no beta-glucosidase was localized in the vacuole.

Journal Article↗
PubMedDate not supplied

[Activity of cathepsin B and serine trypsin-like peptide hydrolases in human kidney extracts].

A potentiality to use the available substrates BAPNA and BAME was studied in estimation of activities of cathepsin B and other trypsin-like hydrolases in extracts of human kidney cortex. In these extracts the BAME-hydrolyzing activity of cathepsin B was difficult if impossible to detect due to high level of attendant non-thiol esterases. At the same time, BAPNA might be used for this purpose as a substrate in estimation of cathepsin B- and trypsin-like peptide hydrolase activities in biopsies of human kidney.

Benzoylarginine-2-Naphthylamide↗
PubMed1992

The human loci DNF15S2 and D3S94 have a high degree of sequence similarity to acyl-peptide hydrolase and are located at 3p21.3.

The short arm of chromosome 3 undergoes genetic loss in most small-cell lung cancers and renal cell carcinomas. The most frequently deleted region includes the DNF15S2 locus (mapped to 3p21), suggesting that a putative recessive tumor-suppressor gene might be located nearby. A cosmid clone, cA476, contains the D3S94 locus and two HTF islands and detects a PstI RFLP. We have isolated cDNAs homologous to conserved fragments within cA476; and these cDNAs have 96% sequence similarity to a cDNA derived from the DNF15S2 locus. Sequence information from cDNAs derived from both the rat and pig acyl-peptide hydrolase (E.C.3.4.19.1) gene show that they have a high degree of sequence similarity to cDNAs derived from D3S94 and DNF15S2, suggesting that they are all the same locus. Cosmid cA476 (DNF15S2) has been mapped, by fluorescent in situ hybridization, to chromosome 3p21.3. D3S94 and DNF15S2 are quite distinct from aminoacylase 1 (ACY1), which has been physically linked to D3S2, D3S92, and D3S93, all localized within 3p21.1.

Animals↗
PubMed1980

Peptide hydrolases of the human small intestinal mucosa: distribution of activities between brush border membranes and cytosol.

Brush border membranes from frozen human small intestine have been purified using a method which did not involve the use of EDTA-containing buffers or the disruption of brush border fragments with high concentrations of Tris. On average a 24-fold increase in specific activity of alpha-glucosidase (brush border marker) was obtained in the final preparation which contained insignificant traces of enzyme marker activities from cytosol and lysosomes. The homogenates of human small intestinal mucosa were shown to contain enzymes capable of hydrolysing di-, tri-, and tetrapeptides as well as amino acid- and peptide-2-nephthylamides. Assuming a 100% location of alpha-glucosidase in the brush border membrane, distribution studies indicated that activities against tetrapeptides and leucyl-2-naphthylamide were located exclusively in the brush border membrane. A large proportion of activity against alpha-glutamyl-2-naphthylamide, gamma-glutamyl-2-naphthylamide and glycyl-prolyl-2-naphthylamide were also recovered in the brush border membrane fraction. Depending on the substrate utilized, 33-87% of tripeptidase activity was located in the brush border membrane. However, 58-87% of dipeptidase activity was recovered in the soluble fraction.

Amino Acids↗
PubMedDate not supplied

[Peptide hydrolase activity in brain tissues during the early stages of post-hypothermia period].

The acid peptidohydrolase activity in the homogenate, dissoluble and mitochondrial-lysosomal fractions of brain tissues of rats who have endured deep hypothermia was determined after their "active" warming for an hour and on the 1st, 2nd, 3d and 7th days after their self-warming. The "active" warming of rats who have endured deep hypothermia (19-20 degrees C) brings about the restoration of the acid peptidohydrolase activity in the subcellular brain tissue fractions. After self-warming the examined enzyme activity restores 7 days later. In the dynamics of the posthypothermic period a change in the acid peptide hydrolase distribution in fractions occurs on the 2nd-3d days.

Animals↗
PubMed1970

The subcellular localization of di- and tri-peptide hydrolase activity in guinea-pig small intestine.

1. Two different subcellular fractionation techniques were applied to guinea-pig intestinal mucosa and the composition of the brush borders prepared by the two methods were compared. 2. By using a kinetic assay system the subcellular distribution of activity against ten dipeptides and five tripeptides was studied. 3. Only small amounts (5-10%) of activity against dipeptides were found in the brush-border region, the enzymes being concentrated in the cytosol. 4. Significant amounts (10-60%) of activity against tripeptides were found in the brush border with the remainder largely present in the soluble fraction. 5. The relevance of these studies to the localization in vivo and the possible role of peptidases in protein digestion is discussed.

Animals↗
PubMed1975

Evidence for two different modes of tripeptide disappearance in human intestine. Uptake by peptide carrier systems and hydrolysis by peptide hydrolases.

The intestinal fate of two tripeptides (triglycine and trileucine), which differ markedly in solubility and molecular weight, have been investigated by jejunal perfusion in healthy human volunteers. Rates of glycine or leucine uptake from test solutions containing triglycine or trileucine were greater than from test solutions containing corresponding amounts of free glycine or free leucine, respectively. The rate of glycine uptake from a 100 mM triglycine solution was greater than that from a 150 mM diglycine solution. At each infused load of triglycine (e.g., 1,000 mumol/min) the rates (micromoles/minutes per 30 cm) of either triglycine disappearance (810 +/- 40) or glycine absorption (2,208 +/- 122) were markedly greater than the luminal accumulation rates of either diglycine (56 +/- 10) or free glycine (110 +/- 18). The luminal accumulation rate of free leucine during infusion of a 5 mM trileucine solution was over threefold greater than that of free glycine during the infusion of a 5 mM triglycine solution. Luminal fluid exhibited no hydrolytic activity against triglycine, but contained some activity against trileucine. Saturation of free amino acid carrier system with a large load of leucine did not affect glycine absorption rate from a triglycine test solution, but isoleucine markedly inhibited the uptake from a trileucine solution. When the carrier system for dipeptides was saturated with a large amount of glycylleucine, the disappearance rate of triglycine was considerably reduced while that of trileucine remained unaffected. After addition of glycylleucine to tripeptide solutions, there was a minimal increase in the luminal accumulation of diglycine, while dileucine accumulation was incresed by 62-fold.

Biological Transport↗