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PubMed1984

[Urinary alanine aminopeptidase excretion in children: reference values and effect of nephrotropic contrast media].

The catalytic activity of alanine aminopeptidase (EC 3.4.11.2) in urine shows a clear cut difference between boys (1530 mU/d X m2) and girls (1143 mU/d X m2). Nineteen children (preterms to 14 years) received contrast media (loxaglate (Hexabrix) (N = 15) or lotalamate (Conray 70) (N = 4] according to the diagnostic indication. The alanine aminopeptidase activity increases to 10-fold of the initial value in the loxaglate and 19-fold of the initial value in the lotalamate group. These results demonstrate a much higher response of the kidney to contrast medium in children than in adults.

Adolescent↗
PubMed1983

Changes in plasma renin activity (PRA), angiotensin I and placental leucine aminopeptidase (P-LAP) activity during normal pregnancy.

Plasma renin activity (PRA) and relative changes in angiotensin I compared with non-pregnant women were determined by radioimmunoassay (RIA) at different stages of normal gestation. Their levels showed increases in the early and late stages, and decreases at the period of 25 to 28 weeks of pregnancy in the middle stage, although their levels were higher than those in non-pregnant women throughout pregnancy. The increase in angiotensin I was less striking than that of PRA. Placental leucine aminopeptidase (P-LAP) activity increased progressively with advancing gestation, reaching the highest value at the 38th week of pregnancy. Simultaneous estimations of changes in angiotensin I and placental leucine aminopeptidase (P-LAP) were performed longitudinally in 12 normal pregnant women. The significance of the increase in P-LAP activity and the relationships among PRA, angiotensin I and P-LAP during normal pregnancy are discussed.

Angiotensin I↗
PubMedDate not supplied

Differentiation of strains of Staphylococcus epidermidis biotypes 1 and 4 by aminopeptidase profiles.

Seven different strains of Staphylococcus epidermidis and one strain of S. aureus were catagorized by their aminopeptidase activity. Eight different profiles were obtained: five profiles for S. epidermidis biotype 4 (each representing a different known serotype), two profiles for S. epidermidis biotype 1 (one for each strain used) and one for the strain of S. aureus used. Despite some similarities, distinct patterns of the hydrolysis of 22 different amino acid-beta-naphthylamides were evident for each individual strain. The evaluation of aminopeptidase profiles provides another means for distinguishing between strains of the same species and can, therefore, be used advantageously and in combination with serotyping as an epidemiological tool.

2-Naphthylamine↗
PubMed1984

Arginine aminopeptidase activity of phytopathogenic spiroplasmas.

The arginine aminopeptidase activity of arginine-utilizing phytopathogenic spiroplasmas was investigated with arginine beta-naphthylamide substrate using the fluorometric method. Hydrolysis of this substrate was demonstrated with broth cultures, washed concentrated whole cells, and cell-free extracts of corn stunt spiroplasma (CSS) and Spiroplasma citri. Growing CSS and S. citri in the presence of 47 mM arginine resulted in a reduction in aminopeptidase activity, indicating that synthesis of the enzyme might be subject to control by catabolic repression. Results of these experiments suggest a possible biochemical basis for pathogenicity of phytopathogenic spiroplasmas in vivo.

Aminopeptidases↗
PubMed1984

Different enzymatic oscillations in vivo caused by the stereoisomers of an aminopeptidase inhibitor, bestatin.

The present study was undertaken to compare the enzymatic oscillations induced in three major organs, spleen, kidney, and liver, of mice by the active and inactive forms of an aminopeptidase inhibitor, bestatin. Although bestatin caused sine curve-type oscillations of enzymatic activities in spleen and kidney, its isomer, possessing no enzyme-inhibiting actions and no biological actions, did not show any typical enzymatic changes. Such typical oscillations were not elicited by either one of those two agents in liver, in spite of the apparent difference in the type of oscillations induced by them in this organ. These observations were taken to indicate that the enzymatic oscillations in vivo caused by bestatin are closely related to its aminopeptidase-inhibiting actions seen in vitro and that the immunomodifying actions of this agent are based on its effects on enzymes sensitive to it, possibly involving immunoresponsive cells.

Aminopeptidases↗
PubMed1984

[Proteases from the enterocytes of the porcine small intestine. Role of aminopeptidase N in the transport of dipeptides].

The kinetics of radioactive label uptake from [U-14C]Gly, L-[4.5-3H]Leu and dipeptide [U-14C]Gly-L-[4.5-3H]Leu by the brush border membrane vesicles of porcine small intestine have been studied. The effect of aminopeptidase N inhibitors and of leucine-binding protein on the accumulation rates has been investigated. A comparison of the kinetic parameters for the uptake and hydrolysis of Gly-L-Leu, has demonstrated that the dipeptide transfer includes two conjugated steps, i. e., hydrolysis catalyzed by aminopeptidase N and transport of the resultant free amino acids by a specific carrier.

Aminopeptidases↗
PubMed1983

Sea urchin sperm aminopeptidase: comparative studies of sperm-associated and -solubilized enzymes.

Aminopeptidase activity was demonstrated in the spermatozoa of the sea urchin, Strongylocentrotus intermedius. The enzyme solubilized from sperm cells was inactivated with bestatin, amastatin, p-chloromercuribenzenesulfonate, ZnCl2, and trypsin, whereas that in the intact cells was scarcely affected by these agents. On the other hand, bestatin ethyl ester inactivated the two enzyme forms to almost the same extent. It also inhibited the fertilization process in this species. These results suggest that the aminopeptidase associated with the spermatozoa is shielded with a permeable barrier and plays some role in fertilization.

Aminopeptidases↗
PubMed1984

A specific kinetic assay for tripeptide aminopeptidase in serum.

This is a method for measuring tripeptide aminopeptidase (EC 3.4.11.4) activity in serum. L- Leucylglycylglycine is used as substrate, and the reaction is followed by monitoring the absorbance increase at 340 nm when NAD+ is reduced to NADH in the presence of an excess of leucine dehydrogenase. This principle allows kinetic determination of the enzyme without interference by carboxypeptidases. Amastatin is added to the reaction mixture to prevent nonspecific hydrolysis of the substrate catalyzed by other aminopeptidases. As final reaction concentrations we recommend (per liter): 100 mmol of Tris buffer (pH 8.2), 4.0 mmol of L- leucylglycylglycine , 10 kU of leucine dehydrogenase, 3.8 mmol of NAD+, and 85 mumol of amastatin . The assay is suited to modern enzyme analyzers and has high precision.

Adult↗
PubMedDate not supplied

[Properties of Streptomyces griseus aminopeptidase].

The paper deals with studying the properties of aminopeptidase isolated from Str. griseus culture fluid. The preparation is characterized by a high specific activity and heat stability, it has no admixtures of carboxypeptidases and proteinases. The enzyme is easily inhibited by EDTA, but the addition of Ca2+ evokes its complete reactivation. A partial recovery of the activity may be also reached under the influence of some other bivalent metals. In hydrolysis of di- and tripeptides it is shown that the enzyme has a preferential effect on the substrates with N-terminal leucine. Peptides with N-terminal alanine, valine and glycine are almost not hydrolyzed. The use of the native insulin and decapeptide with the known amino acidic sequence as substrates shows that aminopeptidase can hydrolyze proteins and peptides with the successive release of some amino acids: phenylalanine, serine triptophane, valine, asparagine, etc. Glycine is difficult for removal and may inhibit the further hydrolysis of the polypeptide chain.

Amino Acids↗
PubMed1981

Characterization and comparison of aminopeptidase activity of various strains of Mycobacterium tuberculosis.

The aminopeptidase activity of three strains of Mycobacterium tuberculosis, H37Rv, H37Ra, and M. tuberculosis from a patient, was partially purified and characterized. The activity from all three organisms was found to be very similar, if not identical. All three aminopeptidases eluted at a similar salt concentration on DEAE Bio-Gel; were active on the same synthetic and peptide substrates; had molecular weights of 75-76,000; were found to be stable between pH 5 and 8, and 4 degrees and 40 degrees C; and had a pH optimum of 7. They were inhibited by low concentrations of Hg2+, Cu2+ and Co2+; metal chelators; and 4-chloromercuribenzoic acid. A number of amino acids and several antibiotics were also found to be inhibitory. Of the antibiotics tested, rifampicin and bacitracin were the most effective.

Aminopeptidases↗
PubMed1982

Sulfhydryl content of bovine eye lens leucine aminopeptidase. Determination of the reactivity of the sulfhydryl groups of the zinc metalloenzyme, of the enzyme activated by Mg2+, Mn2+, and Co2+, and of the metal-free apoenzyme.

The reactivity of the sulfhydryl groups of leucine aminopeptidase from bovine eye lens has been studied by carboxymethylation with iodoacetate of the native enzyme (Zn2+-Zn2+), of the enzyme activated with magnesium (Zn+-Mg2+) or manganese (Zn2+-Mn2+), the enzyme incubated with cobalt (CO2+-Co2+), and the metal-free apoenzyme. The reactivity of the sulfhydryl groups was also determined in the presence of denaturing agents with or without reducing agents. All seven half-cystines per leucine aminopeptidase subunit are in the sulfhydryl form. In the native and the Zn2+-Mn2+ enzyme, only one of the cysteines (residue 344) reacts readily with iodoacetate. In the Zn2+-Mg2+ enzyme, two cysteines react (residues 344 and 412) and in the Co2+-incubated enzyme only one (residue 412). The metal-free apoenzyme has at least three reactive cysteines (residues 344, 412, and 429). The data suggest that sulfhydryl groups are involved in the binding of metal ions.

Amino Acid Sequence↗
PubMed1982

[SH-dependent aminopeptidase from bovine kidney. Isolation, physico-chemical properties and substrate specificity].

The SH-dependent aminopeptidase was isolated from bovine kidney and purified 800-fold. The enzyme has a pH optimum of 7.0 and pI of 5.5 and is activated by dithiothreitol and inhibited by p-chloromercurybenzoate. The enzyme has a molecular weight of 56000 and is represented by four polypeptide chains with m. w. of 14000. Aminopeptidase hydrolyzes beta-naphthylamides of arginine, alanine, leucine and proline and peptides with free N-terminal neutral and basic amino acid residues having L-configuration as well as angiotensin III. The enzyme does not split proteins, angiotensins I and II, B-chains of insulin and peptides with a blocked N-terminal amino group and peptides with proline as a second amino acid from the NH2-end.

Aminopeptidases↗
PubMedDate not supplied

[The activity of urinary cystine-aminopeptidase in normal pregnancy (author's transl)].

Knowing that examining the levels of aminopeptidases in the serum of pregnant women can give us information about normal feto-placental function, we have tried to see if testing for these enzymes in urine of women with normal pregnancies could lead us to a more adequate and easy screening for fetal distress. With this end in view we examined the activity of urinary cystine aminopeptidase (CAP) in a group of 60 pregnant women at different stages of normal pregnancies. This activity was determined on 24 hour specimens of urine collected at different times in pregnancy and the results showed that there were variations from one week to another. As compared with activity in serum in normal pregnancies, urinary activity of this enzyme is raised in the first trimester of the pregnancy and lowered in the last trimester. The explanation of other authors about the possibility of these enzymes with high molecular weights passing into the urine is discussed. Asymptomatic bacteriuria is common in pregnancy, and so it can explain how CAP is excreted in the urine. But this hypothesis has still to be studied and proven.

Adolescent↗
PubMed1982

Partial purification and characterization of four aminopeptidases from the soluble fraction of human placenta.

Four aminopeptidases hydrolysing amino acid-beta-naphthylamides were partially purified from human placental soluble fraction. Separation of the activities, Con-pools I, II1, II2 and III, have not been previously reported. They had apparent molecular weights of 80,000, 100,000, 210,000, and 120,000, respectively. Con-pool II2 seemed to be a glycoprotein. Con-pools I and III were activated by sulphydryl modifiers and inhibited by p-chloromercuribenzoate (p-CMB), properties which indicate their dependence on thiol-groups. Con-pool II1 hydrolysed only arginine- and lysine-beta-naphthylamides. It was inhibited by bestatin and p-CMB. Its special characteristic was activation by monovalent anions, notably chloride ions. These results suggest that Con-pool II1 is aminopeptidase B.

Aminopeptidases↗
PubMed1981

[Modification of blood serum mineral levels and aspartate aminotransferase, leucine aminopeptidase and alkaline phosphatase activity and plasma in glucose levels in healthy cattle by Ca-Mg-containing solutions].

Three high-performance cows in lactation were tested each for the effects of two kinds of infusion each, 500 ml of Tetamag-2 solution (60 g of calcium gluconate and 60 g of magnesium adipate) and 500 ml of Calcimag (100 g of calcium gluconate and 20 g of magnesium adipate), upon the levels of calcium, magnesium, Pa, potassium, and sodium as well as upon the activities of aspartate-aminotransferase, leucine-aminopeptidase, and alkaline phosphatase in blood serum and upon glucose levels in blood plasma. Migration of calcium out of blood plasma was found to take place at much higher rate than that of magnesium. Infusion of Pa and glucose was followed soon by some temporary drop of values. No directional effects were recordable from potassium and sodium. Aspartate-aminotransferase activity did not change in response to transfusion. Intravenous infusion of Tetamag-2 solution caused strong temporary rise in magnesium concentration and, consequently, activation of leucine-aminopeptidase.

Alkaline Phosphatase↗
PubMedDate not supplied

[Effect of SH-reagents and thiol compounds on aminopeptidase from Aspergillus oryzae].

It is shown that iodacetate and iodacetamide produce an insignificant inhibition of the Asp. oryzae aminopeptidase activity, para-chloromercuribenzoate is a stronger inhibitor. Dithiotreitol, beta-mercaptoethanol, reduced glutathione also cause a considerable loss in the enzyme activity. The inhibitory effect is intensified with a combined action of para-chloromercuribenzoate and EDTA. The studies of para-chloromercuribenzoate, iodacetate and iodacetamide effect on the activation of aminopeptidase apoenzyme by cobalt ions showed that the enzyme activity recovery is insignificant. It may be supposed that the enzyme thiol groups are bound with the metal ions necessary for the catalytic activity.

Aminopeptidases↗
PubMed1995

Purification and amino acid sequence of aminopeptidase P from pig kidney.

Aminopeptidase P from kidney cortex was purified in high yield (recovery greater than or equal to 20%) by a series of column chromatographic steps after solubilization of the membrane-bound glycoprotein with n-butanol. A coupled enzymic assay, using Gly-Pro-Pro-NH-Nap as substrate and dipeptidyl-peptidase IV as auxilliary enzyme, was used to monitor the purification. The purification procedure yielded two forms of aminopeptidase P differing in their carbohydrate composition (glycoforms). Both enzyme preparations were homogeneous as assessed by SDS/PAGE silver staining, and isoelectric focusing. Both forms possessed the same substrate specificity, catalysed the same reaction, and consisted of identical protein chains. The amino acid sequence determined by Edman degradation and mass spectrometry consisted of 623 amino acids. Six N-glycosylation sites, all contained in the N-terminal half of the protein, were characterized.

Amino Acid Sequence↗
PubMed1993

Aminopeptidases: towards a mechanism of action.

Aminopeptidases catalyse the removal of amino acids from peptide substrates. Although many functions have been ascribed to these enzymes, lack of knowledge of their complex structure has prevented detailed analysis. Several recent studies have now provided information on the structure and molecular biology of these enzymes, the kinetics of substrate hydrolysis and inhibitor binding. These new data allow prediction of a model mechanism of action for a large subgroup of aminopeptidases.

Aminopeptidases↗