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PubMedDate not supplied

Histochemical study of leucine aminopeptidase in leukemia.

By means of a histochemical method, the leucine aminopeptidase activity was studied in human normal and leukemic peripheral blood. Before administration of cytostatics the enzymic activity was high in the cytoplasm of blasts and in the nuclei of segmented cells. After therapy the activity of leucine aminopeptidase in blasts decreased, while in polymorphs it became negative in nuclei and positive in their cytoplasm. The non-granular leukocytes and platelets displayed a weak enzymic activity both in normal and malignant blood cells. The erythrocytes were negative.

Antineoplastic Agents↗

PubMed1989

xerB, an Escherichia coli gene required for plasmid ColE1 site-specific recombination, is identical to pepA, encoding aminopeptidase A, a protein with substantial similarity to bovine lens leucine aminopeptidase.

The heritable stability of ColE1 is dependent on a site-specific recombination system which acts to resolve plasmid multimers into monomers. This plasmid stabilizing recombination system requires the presence in cis of the ColE1 cer region, plus at least two trans-acting factors encoded by the xerA and xerB genes of Escherichia coli. The xerB gene has been cloned and sequenced and found to encode a polypeptide with a calculated mol. wt of 55.3 kd. The predicted amino acid sequence of this protein exhibits striking similarity to that of bovine lens leucine aminopeptidase (53 kd). The biological significance of this similarity is corroborated by genetic and biochemical evidence which suggests that xerB is identical to the E.coli and S.typhimurium pepA genes that encode aminopeptidase A.

Amino Acid Sequence↗

PubMed1998

[Biosynthesis of leucine aminopeptidase by Xanthomonas rubrilineans 67 in culture with various concentrations of nitrogen containing compounds].

The dynamics of consumption of amine and ammonium nitrogen and glucose in the process of Xanthomonas rubrilineans 67 growth and biosynthesis of leucine aminopeptidase was studied. It was shown that the rate of leucine, alanine and glycine consumption as a source of amine nitrogen out of 16 amino acids was the highest during the fermentation. Addition of these three amino acids or their mixtures to the medium at definite stages of the fermentation process increased the leucine aminopeptidase biosynthesis by 50 to 100 per cent. Ammonium nitrogen was not used by X.rubrilineans 67. The consumption of glucose during the fermentation was even: by the 24th hour of the process the medium contained about 10 per cent of the glucose initial concentration. The optimal temperature for the culture growth and leucine aminopeptidase biosynthesis was determined. It was shown to be 28 degrees C. Higher aeration increased the culture productivity.

Alanine↗

PubMed1992

Isolation of the leucine aminopeptidase gene from Aeromonas proteolytica. Evidence for an enzyme precursor.

The leucine aminopeptidase of Aeromonas proteolytica (EC 3.4.11.10) is a monomeric metalloenzyme having the capacity to bind two Zn2+ atoms in the active site. Structural information of this relatively small aminopeptidase that could illuminate the catalytic mechanism of the metal ions is lacking; hence, we have obtained sequences from the purified enzyme, cloned the corresponding gene, and expressed the recombinant protein in Escherichia coli. The deduced primary amino acid sequence of this secreted protease suggests a potential signal peptide at the NH2 terminus. Expression of the recombinant and native proteins in E. coli and in extracts of culture media of A. proteolytica indicates that the aminopeptidase is secreted as an active and thermosensitive 43-kDa protein that is rapidly transformed to thermostable forms of 30 and 32 kDa. Comparison of the deduced amino acid sequence of the A. proteolytica leucine aminopeptidase with other Zn(2+)-binding metalloenzymes failed to show homologies to the consensus binding sequence His-Glu-X-X-His for the metal ion.

Aeromonas↗

PubMed1982

Localization of leucine aminopeptidase and vitamin B-12 binding protein in rabbit peripheral blood polymorphonuclear leukocytes.

Polymorphonuclear leukocytes were isolated from the peripheral blood of rabbits by Ficoll-Hypaque centrifugation followed by dextran sedimentation. The granulocytes were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrifugation. Leucine aminopeptidase, when assayed with L-leucine-7-amido-4-methyl-coumarin as substrate, showed a similar distribution to N-acetyl-beta-glucosaminidase and thus is localized to the tertiary granules. There was no leucine aminopeptidase associated with the plasma membrane of these cells. Further experiments with purified plasma membranes and inhibitor studies using diazotized sulphanilic acid further confirmed that leucine aminopeptidase had a purely intracellular localization. Vitamin B-12 binding protein showed a similar localization to alkaline phosphatase indicating that, as in human polymorphonuclear leukocytes, vitamin B-12 binding protein is located to the specific granules.

Animals↗

PubMed1981

Inactivation of phagocytosis-stimulating activity of tuftsin by polymorphonuclear neutrophils. A possible role of leucine aminopeptidase as an ecto-enzyme.

The subcellular localization of the tuftsin-inactivating activity was studied using guinea-pig polymorphonuclear neutrophils and the following results were obtained. 1. The tuftsin-inactivating activity was present in the membrane fraction but not in the cytosol and the granular fractions. 2. Intact neutrophils inactivated tuftsin rapidly. However, when neutrophils were modified chemically by a poorly permeant reagent, diazotized sulfanilic acid, the tuftsin-inactivating activity decreased significantly without any inhibition of marker enzymes of cytosol, microsome, granules and mitochondria, suggesting that the tuftsin-inactivating activity is located on the plasma membrane as an ecto-enzyme. 3. When neutrophils were modified by diazotized sulfanilic acid at different concentrations, the tuftsin-inactivating activity of neutrophils was inhibited in proportion to the degree of inhibition of the activity of leucine aminopeptidase, an ecto-enzyme. 4, Hydrolysis of L-leucyl-beta-naphthylamide, a synthetic substrate of leucine aminopeptidase, was inhibited competitively by tuftsin. 5. Treatment of neutrophils with serine protease inhibitors affected neither tuftsin-inactivating nor leucine aminopeptidase activity at all, indicating no involvement of serine proteases, which is said to be located on the cell surface membrane, in the tuftsin-inactivation activity of neutrophils. The possibility was deduced from the above results that leucine aminopeptidase may act as a tuftsin-inactivating enzyme.

Animals↗

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↗

PubMed1976

Leucine aminopeptidase (bovine lens). Effect of pH on the relative binding of Zn2+ and Mg2+ to and on activation of the enzyme.

Incubation of leucine aminopeptidase (bovine lens) (EC 3.4.1.1) with various concentrations of Mg2+ at various pH values in 1 M KCl and 0.155 M trimethylamine-HCl at 37 degrees confirms that Mg2+ competes with Zn2+ for binding only 1 site per 54,000-dalton subunit. The ratio of the apparent association constants (1KZn:1KMg = 1KZn/Mg) at this site (site 1) was estimated to be 20,720 at pH 8.16, 10,570 at pH 8.44, 3,590 at pH 8.78, and 660 AT PH 9.14. The decrease in values of 1KZn/Mg with increasing pH in the activation of leucine aminopeptidase by Mg2+ is attributed to the lowering of the free Zn2+ concentration relative to that of free Mg2+ caused by the formation of ZnOH+ and Zn(OH)2 complexes with increasing OH- concentration. When corrections are made for the binding of Zn2+ by OH- ions, the pH-independent ratio of association constants (1KZn:1KMg = 1KZn/Mg) for the relative binding of Zn2+ and Mg2+ at site 1 of leucine aminopeptidase in 29,800. From the effect of pH on the relative binding constant, a value (beta2) for the product of the two stepwise association constants for the formation of Zn(OH)2 from Zn2+ and OH- (Zn2+ + OH- in equilibrium ZnOH+; ZnOH+ + OH- in equilibrium Zn(OH)2) was estimated to be 4.42 X 10(10) M-2 at 37 degrees. Values of Km at pH 7.5 AND 30 degrees with L-leucine p-nitroanilide as substrate in the presence of 0.01 M NaHCO3 are 4.13 and 2.01 mM for the zinc-zinc and magnesium-zinc enzymes, respectively. Values for Vmax are 0.2 and 2.49 mumol/min/mg, respectively.

Animals↗

PubMed1988

Age-related alteration of renal brush border leucine aminopeptidase in rat kidney cortex.

Renal brush border enzyme activities were significantly decreased with age. The decrease was observed in the homogenate and brush border fractions. Purified leucine aminopeptidase was significantly decreased in Vmax and Km value for leucyl-beta-naphthylamide in the old rats. Heat stability of leucine aminopeptidase from both old and young rats showed biphasic, and the enzyme from old rats was more stable at 60 degrees C than that of the young. However, other properties such as molecular weight, antigenicity, charge, and optimum pH were not significantly different between young and old rats. From these results, it is suggested that age-related alteration of leucine aminopeptidase is due to a conformational change of enzyme molecule; the conformational change might occur at the active sites of the enzyme.

Aging↗

PubMed1975

Potential latentiation forms of biologically active compounds based on action of leucine aminopeptidase. Dipeptide derivatives of the tricycloaliphatic alpha-amino acid, adamantanine.

Some glycine, leucine and phenylalanine dipeptide derivatives of the transport inhibitory, tricycloaliphatic alpha-amino acid, adamantanine (1), have been synthesized using classical methods of peptide synthesis with the aim of improving the latter's bioavailability. Although test doses of glycyladamantanine and L-leucyladamantanine appeared to be absorbed in vivo as evidenced by its appearance in the uring following intraperitoneal administration, they were not hydrolyzed by a purified preparation of leucine aminopeptidase in vitro. Indeed, they were inhibitors of this enzyme. Adamantanylglycine, adamantanyl-L-leucine, and adamantanyl-L-phenylalanine were also not hydrolyzed by leucine aminopeptidase.

Amantadine↗

PubMed1993

Study of activities of arginase, hexosaminidase, and leucine aminopeptidase in prostate fluid.

Our previous studies demonstrated that extracts of the cancerous prostate tissues exhibit increased activities of arginase and hexosaminidase and decreased activity of leucine aminopeptidase. In an endeavor to devise a reliable, noninvasive and cost effective method for the diagnosis of prostate carcinoma, prostate fluids collected from 123 patients were analyzed for arginase, hexosaminidase, and leucine aminopeptidase. Based on the clinical diagnoses, the patients were divided into four groups: 13 men with chronic prostatitis, 29 with no recognized prostatic lesions, 63 with benign prostatic hyperplasia, and 18 with prostate cancer. The prostate fluids had no detectable arginase activity. The means of the total (units/mL) and the specific activities (units/mg of protein) of hexosaminidase and leucine aminopeptidase varied, albeit there were no significant differences in the four groups of patients recruited in this study. It was concluded that the profiles of enzymes in prostate fluids might differ from that in the secreting prostate tissues and that the results of enzyme analysis in prostate fluids for the diagnosis of cancer should be interpreted with caution.

Adolescent↗

PubMed1982

Effect of cryosolvents and subzero temperatures on the hydrolysis of L-leucine-p-nitroanilide by porcine kidney leucine aminopeptidase.

The hydrolysis of L-leucine-p-nitroanilide by porcine kidney leucine aminopeptidase in aqueous mixed-solvent systems containing methanol, ethanol, dimethyl sulfoxide, and dimethylformamide has been investigated in the -30 to -23 degrees C temperature range. At 23 degrees C and pH* values in the 8-10 range, the enzyme is stable for over 25 h in solutions containing 50% v/v of any of these four cosolvents. Measurements of the tryptophan fluorescence of the enzyme at pH* 9.0 confirm that the enzyme is not denatured under these conditions. KM increases exponentially and kcat decreases linearly with increasing cosolvent concentration. Methanol, in particular, has a very small effect on KM. Ultrafiltration experiments demonstrate that there is no dissociation of monomers of the enzyme brought about by the presence of 50% v/v methanol or dimethyl sulfoxide. Preliminary tests with the partition method provide no evidence for an acyl-enzyme intermediate. The effect of pH* on kcat and KM in 50% v/v methanol is very similar to the effect of pH on these kinetic constants in aqueous solution. Lowering the temperature from 23 to 0 degree C does not alter the shape of the pH* profile obtained in 50% v/v methanol. The Arrhenius plot obtained in 50% v/v methanol is linear over the -30 to -23 degrees C temperature range, and the calculated energy of activation, 8.2 +/- 0.8 kcal/mol, is in good agreement with the value of 7.4 +/- 0.7 kcal/mol found for the reaction in aqueous solution. Collectively, these data indicate that methanol is the best cosolvent for cryoenzymological studies, that ethanol and dimethyl sulfoxide are also suitable cosolvents, and that the presence of any of these cosolvents at either ambient or subzero temperatures does not perturb the catalytic pathway.

Anilides↗

PubMed1975

Studies of platinum complex inhibition of leucine aminopeptidase.

The inhibition of swine kidney leucine aminopeptidase by N-alkyl-substituted etyhlenediamine liganded dihaloplatinum chelates has been investigated. The rate of this inhibition at 37 degrees is considerably less than that for the platinum tetra- and hexahalo complexes and also the ethylenediamine dihalo chelates. Only mixed inhibition was observed in these studies. For the time studies used here little if any inhibition occurred at room temperature. L-Methionine and L-Ala-L-Met did not reverse the platinum chelate inhibition nor did they prevent it.

Animals↗

PubMed2006

Leucine aminopeptidases: diversity in structure and function.

Leucine aminopeptidases (LAPs) are metallopeptidases that cleave N-terminal residues from proteins and peptides. While hydrolyzing Leu substrates, LAPs often have a broader specificity. LAPs are members of the M1 or M17 peptidase families, and therefore the LAP nomenclature is complex. LAPs are often viewed as cell maintenance enzymes with critical roles in turnover of peptides. In mammals, the M17 and M1 enzymes with LAP activity contribute to processing peptides for MHC I antigen presentation, processing of bioactive peptides (oxytocin, vasopressin, enkephalins), and vesicle trafficking to the plasma membrane. In microbes, the M17 LAPs have a role in proteolysis and have also acquired the ability to bind DNA. This property enables LAPs to serve as transcriptional repressors to control pyrimidine, alginate and cholera toxin biosynthesis, as well as mediate site-specific recombination events in plasmids and phages. In plants the roles of the M17 LAPs and the peptidases related to M1 LAPs are being elucidated. Roles in defense, membrane transport of auxin receptors, and meiosis have been implicated.

Animals↗

PubMed1990

[Results of clinical and immunoenzymatic studies of neurospecific leucine aminopeptidase in patients with neurologic disorders].

Leucine aminopeptidase of myelin was discovered to contain a protein subunit possessing, in contrast to the main enzymatic mass, antigenic properties and contained by different structures of the central nervous system. The protein was shown to be accumulated by neurons and astrocytes of embryonic tissue culture. The protein was absent from biological fluids of healthy persons and in schizophrenia but it was recordable in the blood and cerebrospinal fluid of patients with different forms of neurological pathology. In patients with neuronal degenerative diseases, the protein level in biological fluids in the terminal stages was significantly lower than in compensated patients.

Alzheimer Disease↗

PubMed1983

Leucine aminopeptidase from human urine.

L-Leucine aminopeptidase has been partially purified from human urine by DEAE-Sephadex and CM-Sephadex chromatography followed by Sephadex G-150 filtration. The specificity toward various substrates, kinetic properties, metal activation and pH activity are reported.

Chlorides↗

PubMed1993

Plasma angiotensin I concentration and serum placental leucine aminopeptidase (P-LAP) activities in puerperal hypertension.

To elucidate the involvement of angiotensin in puerperal hypertension with and without preeclampsia in the course of prior pregnancy, we measured plasma angiotensin I levels and serum placental leucine aminopeptidase (P-LAP) activities in several puerperal hypertensive patients. Placental leucine aminopeptidase (P-LAP) activities of puerperal hypertensive patients with severe preeclampsia during prior pregnancy were equal to or somewhat lower levels than those in normal puerperal women after a normal pregnancy. However, their angiotensin I levels were higher than those in normal puerperal women after a normal pregnancy. In puerperal hypertensive patients with and without preeclampsia during prior pregnancy, P-LAP activities tended to show much lower levels that those in normal puerperal women, while angiotensin I levels tended to show much higher levels than those in normal puerperal women, respectively. Since serum placental leucine aminopeptidase acts as an angiotensinase via degradation of angiotensin III (A-III), our present data suggest the involvement of angiotensin in puerperal hypertension.

Adult↗

PubMed1996

Comparison of leucine aminopeptidase and aminopeptidase III activities in lens.

PURPOSE: To evaluate the relative contribution of leucine aminopeptidase and aminopeptidase III activities to the total aminopeptidase activity in bovine and human lenses under in vivo pH conditions. METHODS: Bovine and human lens extracts were fractionated on a Sephadex G-200 column at pH 6.9 and 8.5 and all the fractions were assayed with Leu-pNA and Arg-pNA as substrates at in vivo lens pH (6.9) and optimum pH for leucine aminopeptidase, (8. 5). The major peptidases were purified and their activities compared with that of LAP and AP III isolated from bovine lens. The ability of bovine and human lens extracts and purified bovine lens LAP and AP III to hydrolyze various peptide bonds in synthetic peptides, VHLPTVEK, bradykinin and Ile-Ser-bradykinin was determined by amino acid analysis of the reaction products. RESULTS: Sephadex G-200 gel chromatography and assay of all the fractions at pH 6.9 showed that the elution volume for the predominant aminopeptidase present in bovine lens extract is the same as that of purified AP III from the same lenses. However, when the assays were done at pH 8.5, the major activity eluting from the Sephadex G-200 column was found in fractions having LAP. A similar study of human lens extracts at pH 6. 9 and 8.5 showed one major peak with elution volume corresponding to that of purified bovine lens AP III: The human lens extracts displayed a very low level of LAP activity. The hydrolysis pattern of peptide substrates by AP III paralleled that of bovine and human lens extract at pH 6.9. The X-Pro bond resistant to LAP in peptide substrate, VHLTPVEK was hydrolyzed by AP III as well as lens extracts. CONCLUSION: Both bovine and human lenses have very low LAP activity compared to AP III activity at in vivo pH 6.9. AP III, by its higher activity, broad specificity and its ability to cleave peptide bonds that are resistant to LAP, is likely to play a major role in lens during epithelial cell differentiation into fiber cells and complete hydrolysis of peptides generated in vivo.

Amino Acid Sequence↗