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PubMed1996

Biology of Amazonian anopheline. XX. Ontogeny of esterases, leucine aminopeptidase and alpha-glycerophosphate dehydrogenase in Anopheles (Nyssorhynchus) darlingi Root, 1926 (Diptera, Culicidae).

The esterases, leucine aminopeptidase and alpha-glycerophosphate dehydrogenase revealed modifications in gene expressions during the development of Anopheles darlingi. The esterases showed five activity bands, 1 and 2 being more deeply stained during the larval stages than in pupae or adults, esterases 3 and 4 more deeply stained in pupae and adults whereas esterase 5 was present throughout development. Leucine aminopeptidase showed five activity bands: LAP2 and LAP5 were characteristic of larvae, LAP3 was specific for pupae and adults, LAP4 was detected only in pupae, and LAP1 and LAP6 were detected in all stages. alpha-Glycerophosphate dehydrogenase presented one activity band on starch gel whose intensity increased with development. Two activity bands were detected on polyacrylamide gel (alpha-GPDH1 and alpha-GPDH2) in 4th-instar larvae (old pigmented larvae) and this activity increased with development.

Animals↗

PubMed1996

[Subcellular distribution of leucine aminopeptidase during the development and aging of rat brains].

INTRODUCTION: The aminopeptidases are considered to be enzymes which can regulate the activity of various neuropeptides. However, their precise function has not yet been fully determined. OBJECTIVE: With a view to studying the function of these enzymes at the cerebral level, the subcellular distribution of soluble leucine aminopeptidase from left and right cerebral hemisphere, in rats of different pre-natal and post-natal ages was determined as described in this paper. MATERIALS AND METHODS: The activity of soluble leucine aminopeptidase was determined fluorimetrically in the sub-cellular fractions obtained from the left and right cerebral hemispheres of rats of different pre-natal and post-natal ages: fetuses (of 19-21 days gestation), 1 week, 1, 5 and 24 months of age. RESULTS: No differences were observed between the cerebral hemispheres at any of the ages studied. However, significant differences were seen in the evolutionary behaviour of the two hemispheres. At all ages, except 24 months, there were significant differences between the fractions. In the fetuses, most activity was seen at the level of the synaptosomal raw fraction and least in the microsomal. At 1-week-old, the highest levels were seen at a microsomal level. In rats of 1 and 5 months of age, the highest levels were detected at synaptosomal level. With regard to the evolution with age, in the homogenate, nuclear fraction, cytosol and mitochondrial fraction a similar profile was observed, with a decrease after birth and an increase at one month, being stable at the other ages. At a synaptosomal level the profile is similar, although the differences are much more marked, with a drastic decrease in activity at two years of age. By contrast, the microsomal fraction showed a very different evolutionary profile with an increase after birth, becoming stable at later ages. CONCLUSIONS: The activity of soluble leucine aminopeptidase shows a heterogeneous subcellular distribution together with significant differences during cerebral development and ageing. The behaviour of this enzyme may reflect the functional state of its neuropeptide substrates.

Age Factors↗

PubMed1979

The origin of human seminal leucine aminopeptidase (LAP).

Examination of the distribution of leucine aminopeptidase (LAP) activity in the male reproductive system showed the existence of the largest amounts of this enzyme in the prostate. Precipitin electrophoresis revealed that seminal LAP is immunologically identical with the prostatic enzyme and distinct from the enzymes in the other male reproductive organs. It was concluded that the origin of seminal LAP is the prostate, by which the enzyme is secreted into the seminal plasma.

Animals↗

PubMed1994

Serum leucine aminopeptidase in head and neck cancer.

Serum leucine aminopeptidase (LAP) activity was assayed in patients with head and neck cancer. The levels were found to be significantly higher than the controls. However, the rise in serum LAP was nearly the same in all patients studied, irrespective of the character or histopathology of the lesion but varied with respect to the site involved, i.e. from about 40 per cent in cancer of the hypopharynx to more than 100 per cent in cancer of the nasopharynx. Serum LAP activity was found to increase with the extent of the lymph node spread. After treatment the levels were found to be reduced.

Biomarkers, Tumor↗

PubMed1976

Leucine aminopeptidase, Significance of serum elevation in bilharziasis.

Leucine aminopeptidase (LAP) activity and creatinine concentration was estimated in serum of twenty five normal adult subjects, twenty four cases with active urinary bilharziasis, eleven cases with active intestinal bilharziasis, ten cases with mixed bilharzial infection (urinary and intestinal), fourteen bilharzial cases with clinical hepato-splenomegaly of bilharzial etiology, thirteen bilharzial cases with clinical hepatosplenomegaly and ascites, and twelve cases with cancer bladder of bilharzial etiology. Significant elevation in the serum enzyme level was found in all bilharzial cases which generally ran parallel to the course of the disease, being more marked in hepatosplenomegalic cases than in cases which showed no clinical signs of liver or spleen involvement. However, it was observed that the enzyme level was lower ascitic than in nonascitic cases. For serum creatinine concentration, no significant variation from normal value was observed in the group of patients with active urinary, active intestinal, mixed infections of bilharziasis and bilharzial hepatosplenomegalic cases. However, a very highly significant decrease in serum creatinine concentration was observed in the group of patients with bilharzial hepatosplenomegaly and ascites. Serum LAP activity and creatinine concentration in the group of patients with cancer bladder of bilharzial etiology showed no statistical variation from normal values.

Adult↗

PubMed1995

Flavonoid inhibitors of trypsin and leucine aminopeptidase: a proposed mathematical model for IC50 estimation.

The inhibitory behavior of flavonoids against trypsin and leucine aminopeptidase followed sigmoidal curves similar to those of any dose-biological response relationship. Statistical analysis using several mathematical equations showed that the relationship may be expressed by a logistic equation, which yielded a high correlation between the experimental data and the predicted results, together with an objective criterion for estimating the IC50 value. Flavones and flavonols exhibited a strong inhibitory effect on trypsin; the presence of hydroxyl groups at positions C-5 and C-7 in ring A is necessary for inhibition of the enzyme, while the simultaneous presence of free hydroxyl groups at positions C-3' and C-4' enhances the inhibitory activity. Inhibition of leucine aminopeptidase by flavonoids does not require 5,7-hydroxylation, but dihydroxylation at C-3' and C-4' and a double bond at positions C-2, C-3 are essential for this activity.

Flavonoids↗

PubMed1980

Beta-hexosaminidase, leucine aminopeptidase, cystidyl aminopeptidase, hepatic enzymes and bilirubin in serum of chronic alcoholics with acute ethanol intoxication.

beta-Hexosaminidase, leucine aminopeptidase, cystidyl aminopeptidase and routine liver parameters are studied in serum of chronic alcoholics with acute ethanol intoxication. The frequencies of pathological serum levels of the routine measurements made are in relatively good agreement with earlier reports. Serum leucine aminopeptidase and cystidyl aminopeptidase did now show any significant aberration in alcoholic liver disease. They correlated well with each other, and gamma-glutamyltransferase. beta-Hexosaminidase activity in serum was increased in almost all patients at the time of admission. All the patients showed decreasing values during the observation period.

Alcoholic Intoxication↗

PubMed2005

Modulation of Streptomyces leucine aminopeptidase by calcium: identification and functional analysis of key residues in activation and stabilization by calcium.

Streptomyces griseus leucine aminopeptidase (SGAP), which has two zinc atoms in its active site, is clinically important as a model for understanding the structure and mechanism of action of other metallopeptidases. SGAP is a calcium-activated and calcium-stabilized enzyme, and its activation by calcium correlates with substrate specificity. In our previous study, we found a non-calcium-modulated leucine aminopeptidase secreted by Streptomyces septatus, the primary structure of which showed 71% identity with SGAP. In this study, we constructed chimeras of SGAP and S. septatus aminopeptidase by using an in vivo DNA shuffling system and several mutant enzymes by site-directed mutagenesis to identify the key residues in this modulation by calcium. We identified the key residues Asp-173 and Asp-174 of SGAP associated with both SGAP activation and stabilization by calcium. We also showed that the known calcium-binding site, which is composed of Asp-3, Ile-4, Asp-262, and Asp-266 of SGAP, only contributes to SGAP stabilization by calcium. Furthermore, we identified an important residue, Glu-196, that functions in cooperation with Asp-173, Asp-174, and calcium to increase the catalytic activity of SGAP.

Amino Acid Sequence↗

PubMed1987

Effect of microsomal leucine aminopeptidase from human placenta (microsomal P-LAP) on pressor response to infused angiotensin II (A-II) in rat.

The role of microsomal placental leucine aminopeptidase (microsomal P-LAP) in the decreased pressor responsiveness to angiotensin II (A-II) in pregnancy was studied. Appreciable amounts of microsomal P-LAP activity were found in rat placenta. The similar dose to the endogenous activity, of human microsomal P-LAP exogenously administered to rats, resulted in significant decrease in the response to A-II. Bestatin, an inhibitor of the microsomal leucine aminopeptidase administered to pregnant rats, enhanced the A-II response. Therefore our present study suggests such refractoriness in response to A-II in pregnancy is due to increased inactivation by the microsomal P-LAP. It was also suggested that prostaglandins were not involved in such refractoriness by the experiments with indomethacin.

Angiotensin II↗

PubMed1997

Bestatin-mediated inhibition of leucine aminopeptidase may hinder HIV infection.

Bestatin, an inhibitor of leucine aminopeptidase (LAPase), significantly decreased HIV infection as reflected by a reduced number of positive immunofluorescent cells, p24 levels, reverse transcriptase activity and the number of proviral copies found in Bestatin-treated cells. Cellular and extracellular LAPase activity in infected cells was higher than the LAPase activity found in uninfected cells. However, cellular and extracellular LAPase activity as well as total protein kinase C activity was lower in Bestatin-treated cells. Conversely, the incubation of human lymphocytic HUT78 cells with LAPase promotes HIV infectivity. The possible role of LAPase in the pathophysiology of HIV was assessed by determining LAPase serum levels in HIV infected patients. LAPase activity levels were three orders of magnitude greater in sera obtained from HIV patients than those detected in sera of uninfected individuals. Although Bestatin reduced HIV infection, a moderate decrease in the reverse transcriptase activity of chronically-infected H9 human T-lymphocytic cells was observed. Based on the higher levels of LAPase present in the serum of HIV patients and on the combined inhibitory effect of Bestatin on LAPase and on protein kinase C activities, we suggest that LAPase may play an important role in the early events of HIV infection such as viral entry.

Anti-HIV Agents↗

PubMed2005

Alteration of leucine aminopeptidase from Streptomyces septatus TH-2 to phenylalanine aminopeptidase by site-directed mutagenesis.

To tailor leucine aminopeptidase from Streptomyces septatus TH-2 (SSAP) to become a convenient biocatalyst, we are interested in Phe221 of SSAP, which is thought to interact with the side chain of the N-terminal residue of the substrate. By using saturation mutagenesis, the feasibility of altering the performance of SSAP was evaluated. The hydrolytic activities of 19 mutants were investigated using aminoacyl p-nitroanilide (pNA) derivatives as substrates. Replacement of Phe221 resulted in changes in the activities of all the mutants. Three of these mutants, F221G, F221A, and F221S, specifically hydrolyzed L-Phe-pNA, and F221I SSAP exhibited hydrolytic activity with L-Leu-pNA exceeding that of the wild type. Although the hydrolytic activities with peptide substrates decreased, the hydrolytic activities with amide and methyl ester substrates were proportional to the changes in the hydrolytic activities with pNA derivatives. Furthermore, based on a comparative kinetic study, the mechanism underlying the alteration in the preference of SSAP from leucine to phenylalanine is discussed.

Aminopeptidases↗

PubMed1960

Improvement in the histochemical localization of leucine aminopeptidase with a new substrate, L-leucyl-4-methoxy-2-naphthylamide.

A new method for the histochemical demonstration of leucine aminopeptidase in fresh frozen sections was developed with the substrate L-leucyl-4-methoxy-2-naphthylamide. The superior enzyme localization is due to the more rapid rate of coupling of the hydrolysis product, 4-methoxy-2-naphthylamine as compared to 2-naphthylamine itself, and to the low lipid solubility and high substantivity for protein of the copper chelate of the dye formed on coupling with tetrazotized diorthoanisidine. A comparison of the old and the new method is illustrated, and a description is given of the localization of leucine aminopeptidase in the tissues of the rat and man.

2-Naphthylamine↗

PubMedDate not supplied

Histoenzymatic activity of leucine aminopeptidase in normal bone marrow cells.

Human, monkey, cat and rat bone marrow cells were studied for the histochemical localization of leucine aminopeptidase activity. The granulocytes have a weak enzymic activity in the immature cells and a very strong one in the differentiated cells. The lymphopoiesis is characterized by a strong reaction in the lymphoblasts and different degrees of the enzyme activity in the lymphocytes. In the erythropoiesis, the undifferentiated cells are strongly positive, while the erythrocytes are negative. The immature and mature cells of the megakariocytic line show a weak leucine aminopeptidase activity.

Age Factors↗

PubMed1989

Immunohistochemical and cytochemical evidences for a possible localization of leucine aminopeptidase in the Merkel cell granule.

Localization of leucine aminopeptidase (LAP) in the Merkel cell-axon complex was studied immunohistochemically and cytochemically in the labial tissues of the mouse, rat, dog, and monkey. Anti-LAP was obtained in rabbits by the injection of commercially supplied swine LAP which was confirmed as electrophoretically pure. The Merkel cells of the mouse, rat, and monkey were positively stained by treatment with anti-LAP but the Merkel cells of the dog were negative. When ultrathin sections of the hair follicle from the rat whisker pad, which contain an abundance of Merkel cells, were processed by immuno-peroxidase or by the immuno-gold method, the reaction products were predominantly deposited on the Merkel cells granules. Furthermore, an immuno-blot assay revealed that an extract of the hair follicles from murine whisker pads contained a molecule of relative molecular mass Mr = 60,000 which is similar in size to a subunit of swine LAP. Thus, it appears that Merkel cell granules of rodents and the monkey contain a protein which resembles lucine aminopeptidase.

Animals↗

PubMed1996

Peptide hydrolysis in lens: role of leucine aminopeptidase, aminopeptidase III, prolyloligopeptidase and acylpeptidehydrolase.

The distribution of leucine aminopeptidase, aminopeptidase III, prolyloligopeptidase and acylpeptidehydrolase activities in different regions of a bovine lens was determined and correlated with the distribution of crystallin fragments (measured as < 18 kDa protein) and water-insoluble proteins in the same lens. A gradient of activity was observed for all the peptidases tested, with the highest specific activity present in the cortical fibers which decreased to one half or below in the inner cortical fibers and nucleus. An inverse correlation between peptidase activities and the amount of crystallin fragments was observed in different regions of the lens. However, a direct correlation between the water-insoluble protein content and the crystallin fragments was observed in all fibers of the same lens. The amount of crystallin fragments and the amount of water-insoluble proteins increased from 2.7% and 8% in the outer cortical fibers to 13% and 68% in the nucleus of the same lens. The water-insoluble fraction from both cortical and nuclear fibers however displayed 4-5 fold more crystallin fragments compared to that present in the water-soluble fraction of the same preparation. When the bovine lens cortical and nuclear extracts were tested for their ability to hydrolyze the peptide substrate, Ile-Ser-bradykinin, the cortical extract was found to be at least ten times superior to the nuclear extract. Prior inactivation of prolyloligopeptidase and other serine proteases by diisopropylfluorophosphate however diminished the ability of the cortical extract to hydrolyze peptide substrates. Bovine lens cortical extract was able to completely hydrolyze alpha-melanocyte stimulating hormone as well as N-Acetyl-Met-Asp-Arg-Val-Leu-Ser-Arg-Tyr showing the presence of active acylpeptidehydrolase facilitating the complete hydrolysis of N-terminally blocked peptides. The human lens extract was found to contain both diisopropylfluorophosphate sensitive and resistant enzymes capable of hydrolyzing peptide substrates.

Amino Acid Sequence↗

PubMed1989

Significance of serum leucine aminopeptidase in tumours of female genital tract.

Serum leucine aminopeptidase (LAP) was estimated in 57 female patients with tumours of the genital tract and compared with 50 age-matched controls. Serum LAP was increased in leiomyomas (p less than 0.01) but significant rise was seen in leiomyosarcomas and endometrial carcinoma of the uterus (p less than 0.001). No increase in serum LAP level, above mean control value was observed in carcinoma of cervix. LAP levels were also increased in cystadenomas of the ovary (p less than 0.01) and highly significant increase, noted in cystadenocarcinomas and dysgerminoma stage III (p less than 0.001). However, no increase of enzyme activity was observed in poorly differentiated papillary carcinoma of the ovary. The serum enzyme level was higher in cystadenocarcinomas as compared to solid ovarian carcinomas in the same clinical stage.

Adult↗

PubMed1975

The release of high-molecular-weight alkaline phosphatase and leucine aminopeptidase into the media of cultured human cells.

Using exclusion from Sepharose 4B as our criterion, we have found a high-molecular-weight form of alkaline phosphatase and of leucine aminopeptidase which are released into the culture media by the FL amnion cell line. A low-molecular-weight form of leucine aminopeptidase is also found to contribute to the total levels of this enzyme in the media. The levels of these enzymes increased during the growth cycle of the culture, paralleling the increase in cell density, suggesting that the two events may be related. This phenomen in culture suggests a possible explanation for the appearance of similar enzyme forms in patient serum and fluids originating from diseased tissue.

Alkaline Phosphatase↗

PubMed1979

Effect of an amino acid imbalance on intestinal sucrase and leucine aminopeptidase activities in rats.

In order to investigate the relationship between dietary amino acids and protein, as well as the activities of intestinal sucrase and leucine aminopeptidase in rats, the effects of an amino acid imbalance on these enzyme activities were studied. The amino acid imbalance was created by adding 8% of an indispensable amino acid mixture lacking threonine to a 6% casein diet supplemented with 0.3% methionine. The food intake and growth of rats fed the imbalanced diet ad libitum were depressed, and the segmental weights of the small intestine and its sucrase activity were clearly lower than those of rats fed the basal diet. The effect of the imbalanced diet under pair-feeding condition on the sucrase activity was similar to that under an ad libitum feeding condition. The food intake and segmental sucrase activity, that is, sucrase activity per length of the small intestine, of rats injected with cortisol (1 mg/day) and fed the imbalanced diet were not depressed, although administration of insulin (1.5 U/day) had no effect on the food intake or segmental sucrase activity. Force-feeding stimulated growth of rats receiving the imbalanced diet, as well as increasing their segmental sucrase activities. The effects of these different conditions on the leucine aminopeptidase activity of rats receiving the imbalanced diet were obscure. These results suggest that changes in segmental sucrase activity might be mediated by stimulating factors in food intake affected by the composition of ingested amino acids and protein together with sucrose in the gastrointestinal lumen.

Animals↗