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PubMed1989

[A membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus. 1. Isolation and purification of the enzyme].

The alanine aminopeptidase of Acinetobacter calcoaceticus was found to be bound to the inner membranes only. The enzyme was solubilized by Triton X-100 and purified approximately 480-fold by gel filtration and affinity chromatography on alanine methyl ketone-AH-Sepharose 4B. The purified alanine aminopeptidase has a molecular mass of 212 kDa, estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme selectively catalyses the hydrolysis of N-terminal alanine residues of peptides. The enzyme is inhibited by p-hydroxy-mercuribenzoate, 1,10-phenanthroline, and puromycin, but was activated by CO2(+)-ions.

Acinetobacter↗
PubMed1989

[A membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus. 2. Substrate specificity of the enzyme].

The substrate specificity of the membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus was investigated with a series of substituted amides of alpha-amino acids. In contrast to mammalian AAP forms, the rate of hydrolysis of the AAP from Acinetobacter calcoaceticus is higher using 4-nitranilide than 2-naphthylamide substrates. The enzyme affinity is very high for alanine substrates and decreases in the series of the amide substituents, from methyl coumarylamides, 4-nitranilides, 4-methoxynaphthylamides to the 2-naphthylamides. The alanine aminopeptidase shows its highest affinity to Ala-MCA (Km = 77 mumol(s)/1).

Acinetobacter↗
PubMed1989

Properties of a novel D-stereospecific aminopeptidase from Ochrobactrum anthropi.

A novel aminopeptidase active toward D-amino acid-containing peptides, D-amino acid amides, and D-amino acid esters has been purified 2,800-fold to homogeneity from a bacterium Ochrobactrum anthropi SCRC C1-38, which had been isolated from soil. The enzyme has a molecular weight of about 122,000 and is composed of two identical subunits (Mr = 59,000). The optimal pH for activity was 8.0. It showed strict D-stereospecificity toward substrates including low molecular weight D-amino acid amides such as D-alanine amide, D-alpha-aminobutyric acid amides, and D-serine amide; D-alanine N-alkylamides such as D-alanine-p-nitroanilide, D-alanine benzylamide, and D-alanine n-butylamide; and peptides with a D-alanine at the NH2 terminus such as D-alanylglycine, D-alanylglycylglycine, D-alanyl-L-alanyl-L-alanine, and D-alanine oligomers. Generally, the enzyme did not act on substrates composed of L-amino acid at the NH2 terminus, although it showed low stereospecificity only toward substrates such as the methyl esters of L-alanine, L-serine, and L-alanine-p-nitroanilide. Comparing the Km and Vmax values for the major substrates, it is clear that the enzyme prefers peptides to amino acid arylamides or amino acid amides. The enzyme was tentatively named as "D-aminopeptidase." EDTA and divalent cations have no effect on the enzyme activity. The enzyme appears to be a thiol peptidase.

Alcaligenes↗
PubMed1986

[Alanine aminopeptidases from small intestinal mucosa of dogs, rabbits and trout. I. Characterization of the "protease forms"].

Alanine aminopeptidases from the mucous membranes of the small intestines of dog, rabbit and trout were concentrated 200 fold in the case of dog and rabbit, and 15 fold in the case of trout. The enzymes were analyzed with respect to substrate specificity, effector behaviour, optimum pH value, Michaelis constants and molecular weight. The values obtained for these enzymes are not consistent in all points with those found for alanine aminopeptidases isolated from the mucous membrane of human jejunum and ileum.

Aminopeptidases↗
PubMed1986

[Alanine aminopeptidase from small intestinal mucosa of dogs, rabbits and trout. II. Behaviour of "detergent forms"].

Alanine aminopeptidases from the mucous membranes of the small intestines of dog, rabbit and trout were purified as detergent forms. The enzymes obtained were characterized with respect to substrate specificity, effector behaviour, Michaelis constants, molecular weight and temperature dependence. In comparison to data of the protease forms of the alanine aminopeptidases, differences could be demonstrated.

Aminopeptidases↗
PubMed1987

Alanine aminopeptidase in serum: automated optimized assay, and effects of age, sex, smoking, and alcohol consumption in a selected population.

In the diagnosis of chronic (as opposed to acute) liver diseases, combinations of indicators are needed to improve specificity. Alanine aminopeptidase (AAP; microsomal aminopeptidase, EC 3.4.11.2) activity in serum reportedly is a very sensitive indicator of intrahepatic cholestasis and biliary obstruction; it is also particularly useful in diagnosing chronic liver disease when combined with an indicator of hepatocyte damage such as aspartate aminotransferase or alanine aminotransferase. We optimized the assay of AAP in serum, automated the assay by using a centrifugal analyzer, then used this automated assay to determine activity in 202 individuals, ages one to 73 years. The preliminary results were analyzed in terms of the effects of age, sex, smoking, and alcohol consumption on AAP activity in serum. Striking sex-related differences were observed: AAP activity in males declined 2.5 times more rapidly with age than did that in females; indeed, activity in adult females remained essentially constant. Moreover, AAP values were higher in men who smoked than in those who did not, the difference being of borderline significance by analysis of covariance (p = 0.0865) but significant by partial correlations (p = 0.02). No similar differences were seen for women smokers and non-smokers. When the effects of other variables were held constant, alcohol consumption alone did not significantly correlate with AAP activity in men or women.

Adolescent↗
PubMed1987

Immunomicroscopic localization of aminopeptidase N in the pig enterocyte. Implications for the route of intracellular transport.

The subcellular localization of aminopeptidase N (EC 3.4.11.2) in the pig enterocyte was investigated by immunofluorescence and immunoelectron microscopy (immunogold staining). By indirect immunofluorescence on either frozen or paraffin-embedded sections, a very intense staining in the microvillar membrane and a weak intracellular staining was demonstrated. No staining was detected in the basolateral membrane. Likewise, the immunogold labelling on Epon-embedded sections was concentrated in the microvillar membrane, whereas the basolateral membrane did not contain significant amounts of labelling. Labelling was demonstrated in the Golgi apparatus and in a minor fraction of the intracellular smooth vesicles positioned between the Golgi apparatus and the microvillar membrane. These observations are compatible with the view that newly synthesized aminopeptidase N is delivered directly to the microvillar membrane by smooth vesicles having a diameter about 70 to 100 nm and does not pass the basolateral membrane on its way to the brush border membrane.

Aminopeptidases↗
PubMed1988

Porcine spleen cathepsin H hydrolyzes oligopeptides solely by aminopeptidase activity.

Cathepsin H purified from porcine spleens was studied for its specificity against various peptide and denatured protein substrates. The enzyme degraded all peptide substrates exclusively by an aminopeptidase activity. The enzyme preferentially released NH2-terminal amino acid residues with large hydrophobic (Phe, Trp, Leu, and Tyr) or basic (Arg and Lys) side chains. Amino acids containing small or polar side chains were not released. Peptides with a proline in the NH2-terminal or penultimate positions were not hydrolyzed either. Large polypeptides such as reduced and carboxymethylated soybean trypsin inhibitor and aldolase were not degraded. These results indicate that cathepsin H is an exopeptidase but not an endopeptidase. We propose that the biological role of this enzyme is the degradation of tissue proteins in lysosomes by its aminopeptidase activity.

Amino Acid Sequence↗
PubMed1986

Manipulation of aminopeptidase activities: differential effects on iontophoretically applied angiotensins in rat brain.

During a recent comparison of iontophoretically applied angiotensin II (ANG II) and angiotensin III (ANG III) in the paraventricular nucleus of the rat we observed that ANG III was more potent than ANG II. This suggested that ANG II may have to be converted to ANG III before it becomes active. To test this hypothesis we performed two experiments. Firstly, we examined the effects of bestatin, an aminopeptidase B inhibitor, on the activity of applied ANG II and ANG III. Next, we monitored the effects of amastatin, a specific aminopeptidase A inhibitor, on the action of coapplied ANG II or ANG III. Bestatin, while having no activity of its own, dramatically enhanced the actions of both ANG II and ANG III. Amastatin, on the other hand, had little effect on ANG III's action and diminished or totally blocked ANG II-dependent activity. Like bestatin, amastatin had no effects alone. In total these results strongly support the notion that ANG II must be converted to ANG III in the brain before it is activated.

Aminopeptidases↗
PubMed1986

Coordinate repression of arginine aminopeptidase and three enzymes of the arginine deiminase pathway in Streptococcus mitis.

Streptococcus mitis contains two arginine aminopeptidases (I and II) as an arginine-supplying system and the arginine deiminase pathway as an arginine-utilizing system. The levels of arginine aminopeptidase I and three enzymes of the arginine deiminase pathway were suppressed by glucose in an apparently coordinate manner. Enzyme II appeared to be constitutive.

Aminopeptidases↗
PubMed1986

[Comparative characteristics of soluble and membrane brain aminopeptidases. I. Isolation, physico-chemical properties, catalytic activity].

The methods were worked out for isolating of the bovine brain soluble and membrane-bound aminopeptidases in highly purified state. One of the stages involved a biospecific-type chromatography on aminohexyl-Sepharose. Both enzymes were found to have equal molecular masses (ca. 100-107 kD) and isoelectric points (pI 4,6). None of the enzymes possessed a subunit structure. Both aminopeptidases were inactivated by omicron-phenanthroline and by an SH-reagent, p-hydroxymercuribenzoate. The catalytic constants for the hydrolysis of a specific substrate, L-leucine p-nitroanilide, were identical for the two enzymes. So far no differences in the physico-chemical or enzymatic properties of the soluble and membrane-bound enzymes were disclosed.

Aminopeptidases↗
PubMedDate not supplied

[Leucine aminopeptidase activity in pain-induced emotional stress].

It is established that leucine aminopeptidase activity during emotional-algesic stress increases in the brain hemispheres, left ventricle and liver of the rats as compared to that of intact animals. Maximum activation of the enzyme in the brain and liver is detected for the first two days after the stress while in the heart - for the whole period of the total stress damages volume development. A conclusion is drawn that the shifts observed in leucine aminopeptidase activity during emotional-algesic stress affect the methionine-enkephalin and leucin-enkephalin ratio.

Animals↗
PubMed1979

[Aminopeptidase activity in "Corynebacterium vaginale" (author's transl)].

Aminopeptidase activity can only be detected in significant amounts in Gram-negative bacteria with a test reaction using L-alanine-4-nitro-anilide as substrate. Corynebacterium vaginale show no aminopeptidase activity even after prolonged reaction times. This indicates surely that this microorganism is nt a Gram-negative bacteria.

Aminopeptidases↗
PubMed1981

[Aminopeptidase N, a marker of the apical pole in thyroid epithelium of swine and in cultured cells].

An aminopeptidase N has been detected by immunofluorescence in the apical plasma membrane of porcine thyroid cells, facing the follicular lumen. Freshly isolated cells obtained by tissue trypsinization have lost their polarity and exhibited a homogeneous enzyme distribution over the whole plasma membrane. In thyrotropin-stimulated cultured cells organized into follicles, the enzyme is localized on the apical cell pole as observed in tissue. In monolayer cells, the enzyme is localized on all the surface facing the medium. In both types of cultures, fluorescence is also observed in intracytoplasmic organelles, probably lysosomes. Aminopeptidase is a marker of the apical part of the thyroid plasma membrane. Its in vitro localization depends upon cell differentiation which is in relation to culture conditions.

Aminopeptidases↗
PubMed1982

[Activity of various phosphatases, leucine aminopeptidase and resorption of L-35S-methionine in the jejunum of birds maintained on diets with different levels of magnesium].

An experiment was carried out with male broiler chicks from hatching up to the age of 56 days, the composition of the ration used being tabulated. The birds were divided into 4 groups: I--controls that were not given Mg; the basic ration for the birds of the second, third, and fourth group was supplied with 100, 300, and 500 mg Mg per kg of feed, respectively, regardless of the fact that it itself a priori contained Mg at the rate of 1100 mg/kg feed. The activity of p-nitrophenylphosphatase, Mg (Na + K), ATP-ase, 5'nucleotidase, and ;eleucine aminopeptidase as well as the resorption--od L35S-methionine were determined. It was found that the addition of 100 mg/kg Mg to the ration containing 1100 mg/kg Mg led to the considerable increase (P less than 0.01) in the activity of p-nitrophenylphosphatase, Mg, (Na + K), ATP-ase, and 5'nucleotidase in the intestinal mucosa. With the higher rates of magnesium with the addition of 300 and 500 mg/kg to the basic ration the activity of the enzymes cited dropped almost to the level which they had in the control group. The activity of leucine aminopeptidase did not show essential changes at the various levels of magnesium. Neither was the level of magnesium itself of any substantial importance for the resorption of methionine in the small intestine of birds.

4-Nitrophenylphosphatase↗
PubMed1984

Electrophoretic variants of alanine aminopeptidase, alkaline phosphatase, and gamma-glutamyltransferase in urine.

The three brush-border enzymes--alanine aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), and gamma-glutamyltransferase (EC 2.3.2.2)--are present in the urine of healthy persons in two variants, a particulate form and a soluble one. They can be separated by electrophoresis in agarose gel and by ultracentrifugation. The particulate forms exhibit similar electrophoretic mobility, but the soluble forms of these brush-border enzymes differ in their electrophoretic mobilities. The enzyme components of the particulate activity can be mobilized by Triton X-100 and trypsin. The electrophoretic mobility of the soluble forms of alanine aminopeptidase and gamma-glutamyltransferase is slowed by neuraminidase treatment. Both forms of gamma-glutamyltransferase are influenced in their electrophoretic mobility by treatment with n-butanol/diisopropyl ether, showing their lipid dependence. These findings enhance our knowledge of the biochemical nature of brush-border enzymes in urine.

Alkaline Phosphatase↗
PubMed1984

[Proteases of swine small intestine enterocytes. Kinetics of substrate hydrolysis and inhibition of aminopeptidase N from brush border vesicles].

The kinetics of hydrolysis of L-leucine p-nitroanilide and some p-nitrophenylalanine dipeptides by vesicular aminopeptidase N from the porcine small intestine brush border membrane was studied. It was shown that the catalytic properties of the vesicular enzyme are very similar to those known for its solubilized counterpart. Both enzymes are inhibited by o-phenanthroline, ZnCl2 and puromycin with Ki = 10(-5)-10(-6) M. The data obtained offer new possibilities for investigating the role of aminopeptidase N in the amino acid and peptide transport across the enterocyte membrane.

Aminopeptidases↗