[The effect of emotional-pain stress on the activity of carboxypeptidase N--the enzyme of neuropeptide processing in the rat brain]

Activity of carboxypeptidase N [correction of H] increased under emotional-algic stress in the rat pituitary gland and hypothalamus. Carboxypeptidase N [correction of H] seems to be involved in development of the stress response, and soluble forms of the enzyme take part in processing of secretory peptides. Membrane-bound forms take part in processing of the neuropeptides specific by their central action.

[The effect of emotional-pain stress and ethanol on carboxypeptidase-N-like activity in rat hypophysis and serum]

Emotional-painful stress and alcohol intoxication activated carboxypeptidase H in the rat pituitary gland. The enzymatic activity was lower in chronic emotional-painful stress and alcohol consumption than that of their single exposure, but higher than that in control rats. In blood serum carboxypeptidase H-like activity was increased after the single emotional-painful stress, while it decreased in chronic stress. Ethanol affected the enzymatic activity in blood serum less significantly than in the pituitary gland.

Pro-carboxypeptidase R cleaves bradykinin following activation

Arginine carboxypeptidase (CPR) is a labile enzyme present in human serum which is unrelated to carboxypeptidase N. In this study we demonstrate that CPR exists in a precursor form in plasma and can be converted to the active form by trypsin and presumable trypsin-like enzymes. The trypsin-generated active form can not only cleave a small synthetic substrate, hippuryl-L-arginine, but can remove terminal arginine from bradykinin.

On the specificity of carboxypeptidase N, a comparative study

The structure of the enzymatically active subunit of human plasma carboxypeptidase N was modeled based on the homology with bovine carboxypeptidase A. The active site of carboxypeptidase N is well conserved in comparison with carboxypeptidase A. From a comparison of energetically favorable binding sites for different atomic probe groups a hypothesis for the differences in substrate specificity between carboxypeptidases A and N was derived. Small synthetic peptide substrates were synthesized to confirm this hypothesis. This study shows that even with very low homology model building by homology can be employed to build models of sufficient quality to aid in drug design.

Degradation of bradykinin in semen of ram and boar

The pattern of bradykinin (BK; Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9)-inact iva ting peptidases in semen of boar and ram was investigated. The degradation of BK in semen was completely abolished by the metalloprotease inhibitors EDTA and o-phenanthroline. Inhibitors of angiotensin-converting enzyme (ACE; EC 3.4.15.1) and phosphoramidon, an inhibitor of neutral metalloendopeptidase (NEP; EC 3.4.24.11), were only partially effective in preventing BK degradation in semen. An additive effect was seen with simultaneous inhibition of both enzymes, resulting in complete abolition of BK degradation. HPLC analysis demonstrated that exogenous BK in semen is cleaved at Gly4-Phe5, Phe5-Ser6 and Pro7-Phe8. These results indicate that NEP and ACE are the main peptidases responsible for rapid BK inactivation in semen. The involvement of other peptidases known to be responsible for BK cleavage in other tissues and body fluids, namely carboxypeptidase N (EC 3.4.12.7), post proline cleaving enzyme (EC 3.4.21.26) and aminopeptidase P (EC 3.4.11.9) was excluded. NEP and ACE were shown to be localized mainly in seminal plasma and to a lesser extent on sperm cells.

Bradykinin metabolism pathway in the rat pulmonary circulation

OBJECTIVE

The contribution made by different enzymes to the degradation of bradykinin in physiological conditions was estimated by examining bradykinin metabolism in rat serum, in the in situ perfused lung and in vivo.

METHODS

Dose-response curves for the hypotensive effect of intra-arterially and intravenously injected bradykinin were obtained in unanaesthetized rats. High-performance liquid chromatography was used to analyse the products of bradykinin breakdown after incubation with rat serum and perfusion through in situ lung preparations.

RESULTS

In rat serum, kininase I degraded 34% and kininase II 11% of bradykinin, no evidence for other activities being detected. In the awake rat, D,L-2-mercaptomethyl-3-guanidino-ethylthiopropionic acid, an inhibitor of kininase I, did not reduce the percentage of bradykinin inactivation in the pulmonary circulation. In the in situ perfused lung 65% of bradykinin was metabolized and the main products were BK1-7, BK1-5 and BK4-9. Enalaprilat (an inhibitor of kininase II) blocked the formation of BK1-7 and BK1-5 and increased the recovery of BK4-9. beta-Mercapto-ethanol, which inhibits aminopeptidase P, and diprotin A, a specific inhibitor of dipeptidylaminopeptidase IV, both reduced the formation of BK4-9. Diprotin A also allowed the recovery of BK2-9. Bradykinin degradation and BK4-9 recovery were not affected by endopeptidase inhibitors.

CONCLUSIONS

Our results show that the main degradation pathway of bradykinin in the lung is through the action of kininase II at the carboxyl terminus, and sequential cleavage by aminopeptidase P followed by dipeptidylaminopeptidase IV at the amino terminus. The amino-terminal degradation of bradykinin represents about 38% of the total lung kininase activity.

[The effect of alcohol consumption on carboxypeptidase N activity in rat brain during chronic emotional-painful stress]

With ethanol consumption, activity of carboxypeptidase H was increased in all the brain regions of rats with chronic emotional-painful stress. The most distinct increase of enzyme activity was found in the striatum membrane fraction and in the hippocampus. Carboxypeptidase H appears to be involved in development of stress reactions under conditions of ethanol consumption via the enkephalinergic system.

[Renal kallikrein-kinin system]

The renal kallikrein-kinin system seems to participate in the regulation of blood pressure, control of sodium and water excretion, renal vascular resistance and renin release. By using ultrastructural immunocytochemistry, in situ hybridization or polymerase chain reaction experiments with the appropriate cDNA probes, kallikrein and kininogen were observed to exist and be synthesized in different types of cells of the nephron. Recently, new finding of a kinin receptor has been reported, since specific kinin receptor antagonists have become available. The localization of components of kallikrein-kinin system in the kidneys and its relation to renal function is discussed.

[Purification and physico-chemical properties of soluble carboxypeptidase N from cat brain gray matter]

Using affinity chromatography on diasorb-L-arginine and polyacrylamide gel electrophoresis, soluble carboxypeptidase H (E. C. 3.4.17.10) has been isolated from cat brain cortex and purified 598-fold with a 16% yield. The enzyme has a molecular mass of 50 kDa, consists of one polypeptide chain, and displays the maximum activity at pH 5.6. Carboxypeptidase H is a thiol-dependent metalloenzyme and contains a Zn2+ ion in its active center. The Km and V values for dansyl-Phe-Leu-Arg are 100 +/- 5 microM and 12.5 +/- 1.4 microM/min/mg of protein, respectively. The existence of two forms of soluble carboxypeptidase differing in isoelectric points and pH optima has been demonstrated. The enzyme with a pI of 4.8 has a pH optimum at 5.5-5.6, while that with a pI of 5.25-at 6.0.

[The subcellular localization of carboxypeptidase N in the substantia grisea of the cat brain]

The activity of carboxypeptidase H in the cat grey matter is established to be connected with microsomes. A possibility to involve carboxypeptidase H to the processing of neuropeptide predecessors in the encephalon is discussed.

Purification and characterization of new arginine esteropeptidase from the soluble fraction of human submaxillary glands

An arginine esteropeptidase was completely purified from the soluble fraction of human submaxillary glands. The molecular weight was calculated to be 12,000, having 2 species of subunits. The study of the effect of inhibitors confirmed the enzyme's serine protease-like characteristics. The best ester and amide substrates were Tos-Arg-OMe and D-Ile-Pro-Arg-pNA, respectively.

Comparative molecular modeling of the active subunit of human kininase I

The structure of the enzymatically active subunit of human plasma carboxypeptidase N was determined by computer aided model building by homology using the structural coordinates from carboxypeptidase A. The active site of carboxypeptidase N has been well conserved in comparison with carboxypeptidase A. Differences in substrate specificity can be explained by the comparison of energetically favorable binding sites for different atomic probe groups.

Metabolism of bradykinin analogs by angiotensin I converting enzyme and carboxypeptidase N

Bradykinin (BK) analogs such as Lys-Lys-BK, des-Arg9-BK and [Leu8]des-Arg9-BK were poor substrates for angiotensin I converting enzyme (ACE), and analogs containing D-Phe7 residues, or a pseudopeptide C-terminal bond, were completely resistant. However, many of these analogs were metabolized by carboxypeptidase N (CPN) including Lys-Lys-BK, [Tyr8(OMe)]BK and D-Phe7-containing analogs, with Km and Vmax values comparable to those for BK. The only analogs completely resistant to both ACE and CPN were the B2 agonist [Phe8 psi(CH2NH)Arg9]BK, the B2 agonist D-Arg[Hyp3,D-Phe7,Phe8 psi(CH2NH)Arg9]BK, and the B1 agonist [D-Phe8]des-Arg9-BK. These data indicate an important role for plasma CPN and vascular CPN-like activity in the metabolism of the widely used ACE-resistant/D-Phe7-containing antagonists of B2 kinin receptors.

Factors affecting peptide catabolism by oral streptococci

The binding of a number of unsubstituted peptides to Streptococcus sanguis and Streptococcus mutans and their subsequent degradation by such cells were examined. Peptides were added to cell suspensions prepared from glucose-limited growth in a chemostat and, at appropriate time intervals, cell-free filtrates were analyzed for peptides and their constituent amino acid residues by high-pressure liquid chromatography techniques. The results indicated that peptide hydrophobicity plays a limited role in peptide binding, but that charge and chain-length are probably important. In S. sanguis, carboxypeptidase activity rapidly released C-terminal arginine (Arg); this amino acid was less rapidly released from the N-terminus but a number of other residues were also released by aminopeptidase activity. When Arg is buried in the peptide, the rate of its release depends upon the number and type of residues between it and the N-terminus. In contrast, S. mutans possessed only weak peptidase activities. The nature of its peptidase activities indicates that S. sanguis can obtain the metabolically important Arg from a variety of peptides.

A new latent arginine esteropeptidase from human submaxillary gland

One of the arginine esteropeptidases in human submaxillary gland was purified from microsomal membranes. The enzyme is inactive in membranes and requires trypsin treatment for its full activation. The trypsin-activated enzyme was purified to homogeneity. Its molecular weight was determined to be 94,000 by SDS-polyacrylamide gel electrophoresis. Among various substrates examined, the obtained enzyme exhibited high specific activities toward Tos-Arg-OMe (esterolysis) and D-Ile-Pro-Arg-pNA (amidolysis). The enzyme was inhibited by some serine proteinase inhibitors, whereas inhibitors of other types of proteinases did not affect or only scarcely affected it. The enzyme appears to be distinct from other arginine esteropeptidases previously described.

The kallikrein-kinin system in the colon and lung fluid from a cribriform degeneration (cri) mutant mouse

The cribriform degeneration (cri) mutant mouse was widely studied in regard to the electrolyte and kallikrein metabolism because of its potentiality as a cystic fibrosis (CF) genetic animal model. In this paper the activity of the kallikrein-kinin system, and the kininase activity and glycoproteins concentration in colon and pulmonary lavage fluid (PLF) in homozygous mutant (cri/cri) and control sibling mice are described. The mutant mice showed a diminished kininogenase and kininase activity and glycoproteins concentrations in both studied organs. It is concluded that a kallikrein-kinin system alteration could be responsible of the cri/cri electrolyte defect.

[Kininase from the Latrodectus tredecimguttatus venom. Characteristics of the enzyme as a thiol endopeptidase hydrolyzing the -Pro7-Phe8- bond of bradykinin]

The nature of the bradykinin (BK)-hydrolyzing (kininase) activity of peptidhydrolase isolated from spider (Latr. tredecimguttatus) venom has been studied. It was found that the BKase activity of the enzyme is fully inhibited by organic mercurials (10(-5)-10(-6) M) as well as by 5,5'-dithiobis(2-nitrobenzoic acid) (10(-7) M); the latter blocks three SH-groups within the enzyme molecule. Serine and metalloproteinase inhibitors have no effect on the kininase activity. Thin-layer chromatography on silicagel revealed that the highly purified enzyme hydrolyzes the -Pro7-Phe8- bond of BK liberating the C-terminal dipeptide, HPhe-ArgOH. Besides, the kininase splits off the C-terminal tripeptide from angiotensin I by hydrolyzing its -Pro7-Phe8-bond. The enzyme does not exhibit any exopeptidase activity with free and N-substituted tri- and pentapeptides. The data obtained suggest that the Latr. tredecimguttatus kininase can be related to thiol endopeptidases hydrolyzing the peptide bonds formed by proline carboxyl.

[Activity of plasma kininase I and kininase II in hypertensive rats]

This study was undertaken to verify the activity of plasma kininases in hypertension. Male Wistar rats (WIS) were used and three models of experimental hypertension were studied: spontaneously hypertensive rats (SHR), renal hypertensive rats, made according to the method of Goldblatt, DOCA-salt hypertensive rats. Normal Wistar rats, nephrectomized rats and sodium-loaded rats were used as control groups. Plasma from these animals was used to evaluate the kininase activities: kininase II activity (KII) was measured by the hydrolysis of hippuryl-L-histidyl-L-leucine (HHL); kininase I activity (KI) was measured by the hydrolysis of hippuryl-L-arginine (HLA) (CN1 activity) and of hippuryl-L-lysine (HLL) (CN2 activity). The three enzyme activities were characterized by their kinetic constants and the inhibitory pattern of various inhibitors. In normal WIS rats, hydrolysis of HHL proceeds with a Km of 2.55 +/- 0.22 mM and at a Vmax of 0.357 +/- 0.017 mumol/min/ml; the enzyme is inhibited by EDTA, 0-phenanthroline and captopril. HLA has a Km of 6.93 +/- 0.32 mM and a Vmax of 0.748 +/- 0.019 mumol/min/ml while the Km and Vmax values of HLL are 35.8 +/- 1.52 mM and 13.11 +/- 0.40 mumol/min/ml. The hydrolysis of both substrates is inhibited by EDTA, 0-phenanthroline and MERGETPA. KII activity is decreased in WKY and SHR rats (Vmax = 0.241 +/- 0.014 and 0.262 +/- 0.011 mumol/min/ml, respectively). In renal hypertensive rats and DOCA-salt hypertensive rats, the KII activity remained unchanged. CN1 activity was increased in 1K, 1C hypertensive animals (Vmax = 0.866 +/- 0.221 mumol/min/ml) and in DOCA-salt hypertensive rats (Vmax = 1.119 +/- 0.049 mumol/min/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Degradation pathway of kinins in tumor ascites and inhibition by kininase inhibitors: analysis by HPLC

We have recently found presence of a high concentration of a novel type of kinin, hydroxyprolyl3-bradykinin (Hyp3-BK) in human tumor ascites in addition to conventional bradykinin (BK). Because of their potential physiological activity, it is of interest to know how these bradykinins can be degraded in ascites. Degradation of two synthetic kinins, BK and Hyp3-BK, added to the ascitic fluid from patients with ovarian carcinoma and hepatoma, were analyzed by reversed phase HPLC. Both kinins were degraded into their desArg9-BK or -Hyp3-BK and desPhe8-Arg-9-BK or -Hyp3-BK products following incubation with the ascitic fluid. The rate of the degradation of BK and Hyp3-BK was the same. The formation of desArg9-BK was completely inhibited by kininase I inhibitor, while the formation of desPhe8-Arg9-BK was not completely inhibited by a kininase II inhibitor. The degradation of both kinins was inhibited completely by EDTA. The results indicate the presence of other metalloprotease(s) which cleaves kinins in the ascitic fluid, in addition to kininase I and kininase II. The carboxypeptidase A and carboxypeptidase B inhibitor, benzyl malic acid, failed to block degradation of both kinins. A rapid cleave of Phe-Arg into Phe and Arg was also found in the ascitic fluid. Thus, the major degradation products of kinins in the ascitic fluid were demonstrated to be either desArg9-BK or Hyp3-BK, desPhe8-Arg9-BK or -Hyp3-BK, phenylalanine and arginine. Lysyl-BK and lysylhydroxyprolyl3-BK were rapidly converted into BK and hydroxyprolyl3-BK by the ascitic fluid.

Inactivation of the vascular permeability-increasing activity of bradykinin by mycoplasmas

Mycoplasma pneumoniae, M. genitalium, M. fermentans, M. hominis, M. salivarium, M. orale, Ureaplasma urealyticum and Acholeplasma laidlawii inactivated the vascular permeability-increasing activity of bradykinin when the mixture of bradykinin and mycoplasma cells was injected after incubation at 37 degrees C for 1 h. Cell components responsible for inactivation of the activity of bradykinin were found to be arginine-specific aminopeptidase and carboxypeptidase.

The molecular defect in a COOH-terminal-modified and shortened mutant of human serum albumin

Albumin Venezia is a fast migrating genetic variant of human serum albumin which, in heterozygous subjects, represents about 30% of the circulating protein. The molecular defect in this variant was studied in a subject possessing an atypical level of the mutant (80% of the total protein) and in other members of his family. Albumins, isolated from the sera of the propositus and his heterozygous relatives, were treated with CNBr and the resulting fragments analyzed by isoelectric focusing. The peptides were then isolated in a homogeneous form by reverse-phase high performance liquid chromatography and submitted to sequence analysis. The results show that albumin Venezia possesses a shortened polypeptide chain, 578 residues instead of 585, completely variant from residue 572 to the COOH-terminal end: sequence: (see text). This extensive modification may be accounted for by the deletion of exon 14 and translation to the first terminator codon of exon 15, which normally does not code for protein. The absence of a basic COOH-terminal dipeptide in the mature molecule can be explained by the probable action of serum carboxypeptidase N. Additional support for such action comes from examination of the remaining 20% of the total albumin of the propositus, which is found to contain an extra Arg at its COOH terminus, probably due to partial digestion by carboxypeptidase N. The low serum level of the variant in heterozygous subjects suggests that the COOH-terminal end of the molecule is critical for albumin stability.

Purification and properties of microsomal carboxypeptidase N (kininase I) in human placenta

Carboxypeptidase N (kininase I, EC 3.4.17.3) was found in human placenta and purified 600-fold. The enzyme was solubilized from membrane fractions with Triton X-100 and was purified by affinity chromatography with histargin, a potent inhibitor of this enzyme. The pH optimum of the enzyme was 7.8. The Km values for L-hippuryl-L-lysine and bradykinin were 1.25 and 0.43 mmol/l, respectively. The apparent molecular mass (Mr) of the enzyme determined by gel filtration was estimated to be 280,000, which is identical to that of the human serum enzyme. We propose that the placenta is a major source of carboxypeptidase N and thus may be involved in the physiological control of fetal circulation by regulating the kallikrein-kinin and renin-angiotensin systems.