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PubMedDate not supplied

[Hydrolysis of peptides by immobilized bacterial peptide hydrolases].

The feasibility of hydrolysis of a mixture of peptides with an enzyme from the bacterium Xanthomonas rubrilineans, displaying a peptidase activity and immobilized on aluminum oxide, was studied. Kinetic schemes and equations allowing for approaching quantitative description of peptide hydrolysis in complex mixtures containing free amino acids and peptides were obtained. It was demonstrated that as a result of hydrolysis, the content of free amino acids in hydrolysates decreased 2.5- to 3-fold and the molecular weight of the constituent peptides, 2-fold.

Aluminum Oxide↗
PubMed1992

Peptidylglutamyl-peptide hydrolase activity of the multicatalytic proteinase complex: evidence for a new high-affinity site, analysis of cooperative kinetics, and the effect of manganese ions.

The multicatalytic proteinase (MCP) complex or proteasome is a major nonlysosomal proteinase of eukaryotic cells. The proteinase can cleave peptide bonds on the carboxyl side of hydrophobic, basic, or acidic amino acid residues. These activities have been referred to as "chymotrypsin-like", "trypsin-like", and "peptidylglutamyl-peptide hydrolase" activities, respectively, and have been shown to be catalyzed at distinct sites. The latter activity is often assayed with the synthetic peptide substrate Z-Leu-Leu-Glu-beta-naphthylamide (LLE-NA). N-tBoc-Ala-Ala-Asp-SBzl is also a substrate for the rat liver MCP, suggesting a broader specificity for cleavage on the carboxyl side of acidic residues than the peptidylglutamyl-peptide hydrolase activity previously reported. The pH optimum is in the range of pH 7.0-7.5. Studies of the dependence of velocity on LLE-NA concentration show (a) that there is a high-affinity site (LLE1) which obeys Michaelis-Menten kinetics with a Km value of approximately 100 microM and (b) that at higher substrate concentrations (LLE2) the curve is sigmoidal, suggesting either allosteric activation of the proteinase at a second site or the involvement of multiple catalytic sites which display positive cooperativity. Activity at the high-affinity site (LLE1) can be distinguished from that of the activity of the LLE2 component by the effect of inhibitors, divalent metal ions, and KCl, as well as by its response to heat treatment. The addition of 1 mM MnCl2 stimulates both LLE1 and LLE2 activities and also permits saturation of MCP with substrate at concentrations of LLE-NA below the solubility limit of this peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1985

The effect of inhibitors of prolyl endopeptidase and pyroglutamyl peptide hydrolase on TRH degradation in rat serum.

The identity of the enzymes catalyzing the degradation of thyrotropin releasing hormone (TRH) in rat serum was investigated by the use of specific inhibitors of prolyl endopeptidase and pyroglutamyl peptide hydrolase. These inhibitors did not protect TRH from degradation, but o-phenanthroline afforded significant protection. The participation of "thyroliberinase", a metalloenzyme which cleaves TRH at the pyroglutamyl-His bond was implied. A coupled assay using the chromogenic substrate pyroglutamyl-His-Pro-2-naphthylamide and excess diaminopeptidase IV was developed to specifically quantitate "thyroliberinase" activity. Rat serum catalyzed the degradation of 67.5 nmoles substrate/ml serum/h. The data indicate that TRH is degraded in rat serum predominantly by "thyroliberinase" and that prolyl endopeptidase and pyroglutamyl peptide hydrolase do not contribute significantly to this process.

Aminopeptidases↗
PubMed1992

Specificity determinants of acylaminoacyl-peptide hydrolase.

In an attempt to explore how specific features of the substrate's primary structure may affect the activity of rabbit muscle acylaminoacyl-peptide hydrolase (EC 3.4.19.1), a number of acetylated peptides containing specific amino acid replacements in specific positions were prepared and compared as substrates for the hydrolase. The principal variants were D-Ala, Pro, and positive charges (His, Arg, Lys); in addition, the effect of the length of the peptide was also investigated in a less systematic manner. The substrates were either prepared by direct acetylation of peptides, by extension of the N-terminus with acetylamino acids or acetylpeptides, activated as N-hydroxysuccinimide esters, or by isolation of the N-terminal peptides from naturally occurring acetylated proteins. It was found that D-Ala on either side of the bond to be cleaved (positions 1 and 2) completely inhibited the enzymatic activity, whereas acetylated peptides with D-Ala in positions 3 or 4 were as good substrates as those containing L-Ala. Peptides with Pro in positions 2 were also inactive, and most of the peptides with Pro in the third position were very poor substrates; only the peptide Ac-AAP gave reasonably high activity (30% of Ac-AAA), which was reduced to 1-2% if additional residues were present at the C-terminus (Ac-AAPA, Ac-AAPAA). The presence of a positive charge in positions 2, 3, 4, 5, and 6 gave strong reduction in hydrolase activity varying with the charge's distance from the N-terminus from 0 to 15-20% of the rates obtained with the reference peptides without positive charges.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMedDate not supplied

[Peptide hydrolases with catalytic dyad Ser-Lys. Similarity and distinctions of the active centers of ATP-dependent Lon proteases, LexA repressors, signal peptidases and C-terminal processing proteases].

It is established that ATP-dependent protease Lon family belongs to the serine-lysine peptide hydrolases clan. Significant similarity of amino acid sequences of proteases Lon and repressors LexA in the regions including the catalytic serine and lysine residues is revealed by comparing primary structures of different families of the enzymes with Ser-Lys catalytic dyad. The both Lon and LexA families are shown to be divided into two subfamilies in accordance with the nature of amino acids in the catalytically active serine environment. Putative DNA binding sites are revealed in proteolytic domains of Lon A subfamily. Similarities and distinctions of the all families peptide hydrolases of the clan in the regions of their active centers are discussed.

ATP-Dependent Proteases↗
PubMedDate not supplied

[Activity of neutral peptide hydrolases and oxidative enzymes in the myocardium and blood during hypoxic hypoxia].

The citric cycle dehydrogenases and neutral peptide hydrolases (NPH) activity was determined in the myocardium and blood serum of Wistar rats under acute and prolonged hypoxic hypoxia. It was shown that the NPH activity and the activity of the most oxidative enzymes change in the same direction during adaptation to the high-altitude conditions. The role of the NPH in the oxidative metabolism reconstruction under acute and chronic hypoxia was discussed.

Adaptation, Physiological↗
PubMed1994

Studies on the specificity of acetylaminoacyl-peptide hydrolase.

In a continuing attempt to explore the types of specificity determinants that may affect protein-protein (peptide) interactions, a number of short (2-5 residues) acetylated peptides have been compared as substrates for the enzyme acetylaminoacyl-peptide hydrolase (EC 3.4.19.1). The reference substrate was Ac-AAAA, and most of the other substrates were derived from this basic structure by single amino acid substitutions. The Km and kcat for the different substrates were determined by standard steady-state kinetics, and the corresponding delta delta GT++ value derived from kcat/Km was used for the comparison, setting delta detal GT++ for Ac-AAAA equal to 0. The best substrates were found to be those containing negative charges (Asp > Glu) or aromatic residues in positions 1', 2', or 3' (delta delta GT++ values of 2-5 kJ); the negative charge provided by the C-terminus of the substrate also appears to be important, since the amide and O-Me ester derivatives caused a change in delta delta GT++ values of -7 to -8 kJ from the reference peptide. The stimulating effect of the negative charges is consistent with the inhibitory effect of positive charges in similar peptides (Krishna RG, Wold F, 1992, Protein Sci 1:582-589), and the proposed active site model incorporates subsites for both charge-charge and hydrophobic interactions. In assessing all the data, it is clear that the properties of the individual substrates reflect the total make-up of each peptide and not only the effect of a single residue in a given position.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylation↗
PubMed1980

Peptide hydrolases of the human small intestinal mucosa: identification of six distinct enzymes in the brush border membrane.

For this investigation highly purified brush border membranes from human small intestine, prepared according to the method described in the preceding paper [1], have been used. Solubilisation of brush border membrane proteins by sodium dodecyl sulphate, Triton X-100 and papain followed by electrophoresis in polyacrylamide gels revealed six distinct peptide hydrolases. These included the enzymes aminopeptidase A (EC 3.4.11.7), dipeptidylpeptidase IV (EC 3.4.14.-), gamma-glutamultranspeptidase (EC 2.3.2.2) and aminopeptidase M (EC 3.4.11.2), which were clearly separable on polyacrylamide gels after solubilisation with Triton X-100 or papain. Activity recovered in the aminopeptidase M peak in the above gel system could be resolved into two distinct peptidases in addition to aminopeptidase M, by SDS-gel-electrophoresis. One of these peptidases was most active towards aliphatic tripeptide (aminopeptidase 1) while the other appeared to be specific for dipeptides (aminopeptidase 2).

Aminopeptidases↗
PubMedDate not supplied

[Protein content and activity of peptide hydrolases in subcellular fractions of the hypothalamus at various levels of feeding motivation].

After 3-days fasting the specific activity of neutral peptide-hydrolases decreased in the homogenate and nuclear fractions and increased in the mitochondrial and soluble ones. After 5-7-days fasting the above peculiarity persisted. Under the diet recovery specific enzyme activity was recovered up to the control level on the 30th day only. The obtained data prove an intensive renewal of the neutral and acid proteins in the subcellular hypothalamic structures depending on different levels of feeding motivation. This increased functional activity of proteinases is aimed at providing for informational and intracellular processes comprising energetic and structural plasticity of the neuronal organizations of the hypothalamic functional feeding system.

Animals↗
PubMed1982

[Peptide hydrolases of lactobacilli of the Thermobacterium group. I. Demonstration of these activities in Lactobacillus helveticus, L. acidophilus, L. lactis and L. bulgaricus].

The intracellular peptide hydrolase activities of Lactobacillus helveticus, L. acidophilus, L. lactis, and L. bulgaricus were determined using various aminopeptidase, dipeptidase, and carboxypeptidase substrates in addition to casein and whey protein fractions. The different activities were then separated using disc gel electrophoresis. Each bacterium had aminopeptidase activity towards various amino acid beta-naphthylamides and dipeptides. The four species also showed bands of true dipeptidase activities on a large number of dipeptides. Intracellular enzymes from thermophilic lactobacilli also hydrolysed the whey proteins (alpha-lactalbumin and beta-lactoglobulin). From the results of electrophoresis on beta-casein and alpha s1-casein it was shown that beta-casein was totally hydrolysed by L. lactis while it was only partially hydrolysed by the intracellular enzymes of L. acidophilus and L. bulgaricus. On the other hand, alpha s1-casein was only partially hydrolysed by L. helveticus, L. lactis, and L. bulgaricus.

Aminopeptidases↗
PubMed1990

Mucosal peptide hydrolase and brush-border marker enzyme activities in three regions of the small intestine of rats with experimental uraemia.

1. The activities of nine peptide hydrolases and three non-peptidase brush-border marker enzymes have been quantified in crude homogenates prepared from the proximal, mild and distal regions of small-intestinal mucosa for sham-operated (n = 9) and uraemic (n = 14) rats. Abnormalities in enzyme activities were observed in all regions studied in the uraemic group, although no reduction in food intake occurred. 2. The proximal region of the small intestine from uraemic rats showed a general fall in enzyme activities associated with the brush-border. This fall was combined with a decline in mucosal protein content. In contrast, the mid and distal regions showed increased activity against the dipeptide tyrosyl-glycine. 3. It is proposed that the fall in brush-border enzyme activities in the proximal small intestine of uraemic rats is a response to the increased water intake associated with this, and presumably other, rat models of uraemia. The increased enzyme activity against tyrosyl-glycine found in the mid and distal regions of the small intestine of uraemic rats may be caused by an increased small-intestinal transit rate, but could be an attempt to maximize tyrosine absorption in response to decreased plasma tyrosine levels. 4. This study casts doubt on specific activities being the most useful units of enzyme activity, when measured in crude homogenates prepared from the proximal small intestine of uraemic rats. It also demonstrates that enzyme activities measured at a single site in the small intestine of uraemic rats may not be representative of the enzymatic changes occurring in the small-intestinal mucosa as a whole.

Animals↗
PubMed1970

Peptide hydrolase activity of human intestinal mucosa in adult coeliac disease.

The levels of two peptide hydrolases were studied in intestinal mucosa from normal subjects, patients with untreated coeliac disease, and treated patients. The mucosa from the untreated patients had significantly reduced activity against glycyl-glycine and leucylleucine. No such difference was found for the treated patients and it was concluded that the reduction in peptidase activity was secondary to the mucosal damage.

Adult↗
PubMedDate not supplied

[Neutral peptide hydrolase activity in human blood in hypoxia].

Athletes were taken to an altitude of 2100 m and allowed to get adapted to the highland environment for a month. Then blood serum neutral peptide-hydrolases were measured at rest and after exercise. Also, metabolic and respiratory parameters were investigated. In response to identical workloads some subjects showed a decrease (Group 1) while others showed an increase (Group 2) of proteolytic activity. Group 1 subjects exhibited high reactivity of the respiratory system whereas Group 2 subjects showed enhanced anaerobic glycolysis.

Altitude Sickness↗
PubMed1975

[Peptide hydrolase activity during embryonic carp development].

It was established that in the carp the process of embryonic and early postembryonic development was accompanied by the increase in the activity of both the trypsin- and chemotrypsin-like peptide hydrolases. This increase is most evident in larvae with resorbing yolk. The total and protein nitrogen content suffers no changes during embryonic and early postembryonic development. The content of non-protein nitrogen increases from the stage of the middle of segmentation on attaining the maximum level in larvae with resorbing yolk.

Animals↗
PubMed1975

The activity of some peptide hydrolase enzymes in fresh and stored poultry semen from full sib groups of males and their relationship to fertility.

The seminal plasma and sperm of fresh and stored poultry semen were analyzed for the presence of eight peptide hydrolase enzymes. Five enzymes: carboxypeptidase A, carboxypeptidase B, chymotrypsin, glycylglycylglycine hydrolase and pepsin were not present in either plasma or sperm. An aminopeptidase-like and a cathepsin-like activity were found in seminal plasma and sperm while a trypsin-like activity was found in sperm only. There was a significant difference between full sib groups with respect to aminopeptidase-like activity in fresh and stored plasma, while storage for 24 hours resulted in a significant increase in trypsin-like activity of sperm. The aminopeptidase-like activity of fresh sperm was positively correlated with duration and percent fertility of fresh semen, while neither cathepsin-like activity nor trypsin-like activity were correlated with fertility of fresh or stored semen except for a positive correlation between the cathepsin-like activity of fresh plasma and percent fertility of fresh semen.

Aminopeptidases↗
PubMedDate not supplied

[Polyamines and activity of acid peptide-hydrolases in hyperoxia].

The content of spermidine and spermine polyamines in the rat brain under hyperoxic convulsions and four hours after convulsions decreases sharply. The intraperitoneal administration of polyamines before hyperbaric oxygenation decreased the rate of development of hyperoxic convulsions in rats. In the model experiments polyamines prevented changes in the acid peptide-hydrolase activity in the lysosomal and soluble fractions, which occur under hyperoxia.

Animals↗
PubMed1993

Cloning of the PABA peptide hydrolase alpha subunit (PPH alpha) from human small intestine and its expression in COS-1 cells.

PABA peptide hydrolase (PPH) from human enterocytes is comprised of two subunits, alpha and beta. PPH alpha is over 70% identical to meprin, a protease isolated from mouse and rat kidney. The enzyme shows a modular organization in that it contains an astacin protease domain, an adhesive domain, an EGF-like domain, an a putative C-terminal membrane spanning domain. Expression of a chimeric meprin-PPH alpha cDNA in COS-1 cells led to the synthesis of immature, transport-incompetent homodimers. In addition, complex glycosylated forms were detected in the culture medium, suggesting that the enzyme is secreted after proteolytic removal of the membrane anchor.

Amino Acid Sequence↗