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At least 1,063 records · Page 59Linked to original sources
PubMed1992

Localization and characterization of aminopeptidase P in bovine adrenal medulla.

Aminopeptidase P (EC 3.4.11.9) is demonstrated for the first time in the cytosolic fraction of chromaffin cells of the bovine adrenal medulla. The enzyme is inhibited by metal chelators and by sulfhydryl-reactive agents, which suggests that both a tightly bound metal ion and a cysteine residue are necessary for enzymatic activity. Aminopeptidase P might be important for the modulation of the biological activity of neuropeptides. Its occurrence in the adrenal chromaffin cells provides a useful tool for studying the function of this unique proline-specific peptidase in neuropeptide processing and secretion.

Adrenal Medulla↗
PubMed1992

The significance of aminopeptidases and haematopoietic cell differentiation.

Aminopeptidases are a group of enzymes found on the cell surface and in the cytoplasmic compartments of many peripheral blood cell types and their progenitors. Their functional roles include the hydrolysis of several biologically active peptides and growth factors and some have proved to be of diagnostic and prognostic value in leukaemia. These enzymes may also be found in serum as a consequence of non-haematopoietic related diseases and so have been used as indicators of liver damage. Haematopoietic cells in the bone marrow go through a process of growth and differentiation before being released into the peripheral circulation where they fulfill many functional roles. The enzyme activities of some aminopeptidases have been shown to modulate the growth of these cells. In addition, the activities of these enzymes themselves can be regulated by haematopoietic growth factors. However, the mechanisms that regulate their expression and activity are not fully understood. In this report the current literature has been reviewed for evidence of expression, regulation and clinical significance.

Aminopeptidases↗
PubMed1980

Effect of sucrose refeeding on disaccharidase and aminopeptidase activities of intestinal villus and crypt cells in adult rats. Evidence for a sucrose-dependent induction of sucrase in the crypt cells.

In order to gain more insight into the adaptative mechanism of intestinal enzymes to dietary factors in rats, modifications in the activities of disaccharidases and aminopeptidase were measured after refeeding of a 70% solution of sucrose for 15 h following a 2-day fast. Mature epithelial cells from the villus and immature cells from the crypt were isolated after sequential removal of the cells along the villus-crypt axis. Synthesis of brush border disaccharidases was determined by measuring [3H]valine incorporation into proteins. 1. In the whole mucosa, a highly significant increase in sucrase and maltase activities and a significant drop in aminopeptidase activity was observed in the brush border membranes after sucrose refeeding. 2. Stimulation of sucrase and maltase activities in sucrose refed rats was produced mainly in the immature cells of the crypt and lower villus compartment. 3. After separation of the brush border proteins by SDS gel electrophoresis from villus and crypt cells of sucrose refed rats, major incorporation of the radioactive precursor occured in the protein bands corresponding to sucrase and maltase activities of the lower villus and crypt cell brush borders. These findings demonstrate that sucrase stimulation by sucrose occurs mainly in the immature epithelial cells and that the substrate induces de novo synthesis of sucrase molecules.

Animals↗
PubMed1995

An aminopeptidase P from Lactococcus lactis with original specificity.

An aminopeptidase P (E.C. 3.4.11.9) that cleaves the Arg-1-Pro-2 bond of bradykinin has been isolated for the first time from Lactococcus lactis. The peptidase was purified to homogeneity in a 3-step procedure and characterized. It is a monomeric metalloenzyme with a 43 kDa molecular mass, activated by Mn2+ and inhibited by DTT. It differs from the majority of aminopeptidases P already described by displaying a specificity for X-Pro-Pro N-terminal and probably an extended binding site that could accommodate amino acid residues beyond the P'2 position of the substrate.

Amino Acid Sequence↗
PubMed1979

Alanine aminopeptidase activity and autolysis in the tails of Rana catesbeiana larvae during metamorphosis.

1. Alanine aminopeptidase activity and autolysis increase concomitantly in tail tissue of Rana catesbeiana tadpoles during metamorphosis. 2. significant increases first appear at Taylor and Kollros state XX and coincide with the beginning of tail regression as determined by the tail wt body wt ration. 3. The results suggest a role of alanine aminopeptidase in the mechanism of tail resorption.

Aminopeptidases↗
PubMed1991

Aminopeptidase activities present in tissues of Helix aspersa.

1. Tissues of Helix aspersa have been examined for the presence of aminopeptidase activities. 2. Enzyme activities were detected using synthetic peptide substrates containing the fluorescent leaving group 7-amino-4-methyl coumarin. The methods used included continuous fluorimetric assay and activity staining of enzymes in non-denaturing polyacrylamide gels. 3. Several types of peptidase activity were detected, including three distinct aminopeptidases which differ in molecular size and substrate preference.

Amino Acid Sequence↗
PubMed1994

Inactivation of chemotactic peptides by aminopeptidase Ey from hen's (Gallus gallus domesticus) egg yolk.

Aminopeptidase Ey, purified from hen's (Gallus gallus domesticus) egg yolk, was studied for its specificity against N-blocked peptides. Only N-formylmethionyl peptides were hydrolyzed by the enzyme in the tested peptides. N-Formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) lost its chemotactic activity toward human neutrophil after incubation with aminopeptidase Ey.

Amino Acid Sequence↗
PubMed1982

Release of acetylcholinesterase and aminopeptidase in vivo following infusion of amphetamine into the substantia nigra.

Push-pull cannulae were implanted acutely in both substantiae nigrae and both caudate nuclei of the rabbit under urethane anesthesia. Direct infusion of d-amphetamine (10(-6) M) to one substantia nigra evoked a release of acetylcholinesterase and aminopeptidase not only locally, but also from the contralateral caudate nucleus and substantia nigra. The spontaneous release of acetylcholinesterase was reduced in the ipsilateral caudate nucleus. Gel electrophoresis showed that only one molecular form of each enzyme was released. Since the electrophoretic mobilities of these two enzymic activities were different, the released acetylcholinesterase and aminopeptidase belong to separate molecular species. As amphetamine is known to modify dopamine metabolism the evoked release of these two enzymes is probably related to the dopamine-containing nigrostriatal system.

Acetylcholinesterase↗
PubMed1992

Sequence of a gene (lap) encoding a 95.3-kDa aminopeptidase from Lactococcus lactis ssp. cremoris Wg2.

A gene (lap) coding for a Lactococcus lactis ssp. cremoris Wg2 aminopeptidase was cloned from genomic libraries of size-fractionated lactococcal DNA. The 5' end of the lap gene was isolated by using a polymerase chain reaction hybridization probe of 77 nucleotides (nt) synthesized from two degenerate primers derived from the N-terminal amino acid (aa) sequence of the lactococcal lysine-aminopeptidase (LAP). The remaining part(s) of the gene were recovered by a search for overlapping sequences in Southern blots of variably restricted genomic DNA. The complete nt sequence of the lap gene has been determined. A large open reading frame of 2538 nt is predicted to encode a polypeptide of 846 aa (approx. 95.3 kDa; pI, 5.93). A recombinant plasmid containing the lap gene with its flanking sequences was shown to direct in vivo synthesis of LAP activity in Escherichia coli, indicating that the cloned DNA fragment is the lap gene. Primer extension analysis of lap mRNA and Northern blot hybridization indicated the gene transcript to be approx. 3.0 kb in size with a 5'-untranslated region of 19-22 nt. Comparison of the deduced aa sequence indicates that the LAP has extensive homology with the super family of Zn(2+)-metallohydrolases and shows identity in the core deca-peptide consensus sequence for the Zn(2+)-binding motif of these enzymes.

Amino Acid Sequence↗
PubMed1995

Sequence analysis, distribution and expression of an aminopeptidase N-encoding gene from Lactobacillus helveticus CNRZ32.

Lactobacillus (Lb.) helveticus CNRZ32 possesses a 97-kDa metalloenzyme with aminopeptidase activity (PepN; EC 3.4.11.2). A 3.8-kb fragment encoding PepN was cloned into pIL253 and designated pSUW34. Transformation of lactococcus (Lc.) lactis LM0230 with pSUW34 resulted in > 180-fold increase in general aminopeptidase (AP) activity using L-lysine-p-nitroanilide. Southern hybridization was conducted to determine the distribution of homology to the CNRZ32 pepN gene among lactic-acid bacteria (LAB). Hybridization was observed with strains of lactobacilli, pediococci, leuconostoc, streptococci and lactococci. The pepN gene was sequenced and found to encode a protein containing 844 amino acid (aa) residues. A comparison of Lb. helveticus CNRZ32 pepN to Lb. delbrueckii ssp. lactis DSM7290 pepN indicated 69.5% nucleotide (nt) identity and 71.8% aa identity, while comparison to pepN from Lc. lactis ssp. cremoris MG1363 indicated 61.1% nt identity and 49.2% aa identity. Alignment of peptidase aa sequences of LAB, Escherichia coli, yeast and mammalian origin display homology in the zinc-binding domain, as well as a conserved region upstream from the putative active site.

Amino Acid Sequence↗
PubMed1991

Determination of biocatalyst consumption in an aminopeptidase process using automated sample preparation and high-performance liquid chromatography.

A rapid and sensitive method has been developed for the determination of the biocatalyst consumption in the chemo-enzymic production of optically pure natural and synthetic alpha-H-amino acids. It is based on automated sample preparation from an enzymic reaction mixture, reversed-phase high-performance liquid chromatographic separation, post-column reaction and fluorimetric detection. The assay procedure has been applied to the enzymic conversion of racemic norvaline amide into L-norvaline, catalysed by an L-specific aminopeptidase from Pseudomonas putida. Both norvaline amide and norvaline can be analysed in a single assay in the low nanogram range. The method yields reproducible results and requires 30 min from the time of sampling the enzymic reaction mixture to quantitation. The reaction mixture is automatically sampled and analysed several times during the course of the reaction. With the results obtained a conversion curve can be constructed from which the exact biocatalyst consumption can be calculated. By adaptation of the mobile phase, the method can also be applied to other amino acid amides used as substrates in the aminopeptidase reaction.

Aminopeptidases↗
PubMed1991

An enkephalin degrading aminopeptidase of human brain preserved during the vertebrate phylogeny.

1. A soluble human brain aminopeptidase which hydrolyses the Tyr-Gly bond of Met-enkephalin and Leu-enkephalin was identified in the brains of the following vertebrates: mammals (Callithrix jacchus and Rattus norvegicus), bird (Gallus domesticus), reptile (Tupinambis teguixin), amphibia (Bufo paracnemis), fish (Sarotherdon niloticus) and elasmobranchy (Galeocerdo cuvieri). 2. The properties of this enzyme are: molecular weight near 100,000 Da, isoelectric point near 4.9, optimum pH near 7.5, activation by dithiothreitol, strong inhibition by Cu2+, Zn2+, Ni2+, puromycin and bacitracin, hydrolysis of enkephalins and basic and neutral aminoacid-beta-naphythylamide substrates. 3. The results indicate the preservation of this human brain aminopeptidase during the course of vertebrate phylogeny.

Amino Acid Sequence↗
PubMed1987

Purification and characterization of thiol aminopeptidase from the cytosolic fraction of human placenta.

A thiol-dependent aminopeptidase was purified from the cytosolic fraction of human placenta. The purified enzyme consisted of a single polypeptide chain with a mol wt of 95,000. The enzyme was most active in the neutral region with Ala-pNA as substrate, and the activity was increased about 20-fold in the presence of some -SH compounds. The results of substrate specificity studies indicated that the enzyme hydrolyzes bonds involving the amino groups of neutral and basic amino acid residues. However, higher thiol-dependent activity was only detected with neutral ones. The enzyme was strongly inhibited by microbial aminopeptidase inhibitors, puromycin, o-phenanthroline, and sulfhydryl reactive-reagents. As to several naturally occurring peptides tested, the enzyme showed N-terminal Tyr-releasing activity toward enkephalins and kinin-converting activity.

Aminopeptidases↗
PubMed2005

Aminopeptidase P isozyme expression in human tissues and peripheral blood mononuclear cell fractions.

Aminopeptidase P (APP) isoforms specifically remove the N-terminal amino acid from peptides that have a proline residue in the second position. The mRNA levels of three different isoforms, each coded by a different gene, were determined in 16 human tissues and in peripheral blood mononuclear cell (PBMC) fractions by RT-PCR. The cytosolic isoform, APP1, and the cell surface membrane-bound isoform, APP2, are expressed in all of the human tissues and PBMC fractions examined. The very high expression of APP2 mRNA in kidney compared to other tissues was confirmed by enzyme activity measurements. Among the PBMC fractions, APP2 expression is highest in resting CD8(+) T cells, but decreases in these cells following their activation with phytohemagglutinin; in contrast, expression of APP2 increases in CD4(+) T cells upon activation. The third isoform, APP3, is a hypothetical protein identified by nucleotide sequencing. A detailed analysis of its amino acid sequence confirmed that the protein is an aminopeptidase P-like enzyme with greater similarity to Escherichia coli APP than to either APP1 or APP2. Two splice variants of APP3 exist, one of which is predicted to have a mitochondrial localization (APP3m) while the other is cytosolic (APP3c). Both forms are variably expressed in all of the human tissues and PBMC fractions examined.

Alternative Splicing↗
PubMed2004

Gene cloning and overproduction of an aminopeptidase from Streptomyces septatus TH-2, and comparison with a calcium-activated enzyme from Streptomyces griseus.

An aminopeptidase secreted from Streptomyces septatus TH-2 (SSAP) was identified as a heat stable enzyme, and the Ssap gene was cloned and sequenced. The primary structure of SSAP showed 71% identity with that of a Streptomyces griseus aminopeptidase (SGAP), however, it lacked a unique calcium binding site. The recombinant SSAP was overexpressed in the culture supernatant of Escherichia coli harboring pET-KmS2. A comparison of recombinant SSAP and SGAP showed that both enzymes are different in terms of modulation by calcium and substrate specificity. The activity of SSAP was not modulated by calcium, while SGAP is a calcium-activated enzyme. SSAP catalyzed the hydrolysis of L-Lys-pNA efficiently whereas the reaction rate for L-Lys-pNA hydrolysis of SGAP was significantly low. Furthermore, in SGAP, the presence of Ca2+ decreased the reaction rate of L-Lys-pNA hydrolysis. SSAP also had different pKas s of reaction from that of SGAP, although almost all the residues which compose the active site were conserved in both enzymes. This result indicates that SSAP has a different environment of substrate binding and active sites from those of SGAP.

Amino Acid Sequence↗
PubMed2006

A phosphonamidate containing aromatic N-terminal amino group as inhibitor of leucine aminopeptidase-design, synthesis and stability.

Fully deprotected phosphonamidate dipeptides, predicted as effective inhibitors of cytosolic leucine aminopeptidase, showed unexpected instability in water solution at pH below 12. Their hydrolysis rate was strictly correlated with basicity of the N-terminal amino group. To improve this feature a phosphonamidate analogue containing less basic, aromatic 2-aminophenylphosphonate residue in P1 position of the inhibitor was designed. The target compound was synthesised starting from diethyl 2-nitrophosphonate in several step procedure. The decrease in basicity of the terminal amino moiety of the modified analogue in fact resulted in satisfactory improvement of hydrolytic stability of the P-N bond. The developed phosphonamidate was proved to be fully resistant to hydrolysis above pH 7. Surprisingly, tested in enzymatic assays towards leucine aminopeptidase (optimum pH 8.5), it did not exhibit inhibition activity up to milimolar concentration. The explanation could be that diminishing the basic character of the terminal amino group may result in a change of its affinity towards the zinc ions.

Drug Design↗
PubMed2004

The C. elegans methionine aminopeptidase 2 analog map-2 is required for germ cell proliferation.

We have investigated the physiological function of type 2 methionine aminopeptidases (MetAP2) using Caenorhabditis elegans as a model system. A homolog of human MetAP2 was found in the C. elegans genome, which we termed MAP-2. MAP-2 protein displayed methionine aminopeptidase activity and was sensitive to inhibition by fumagillin. Downregulation of map-2 expression by RNAi led to sterility, resulting from a defect in germ cell proliferation. These observations suggest that MAP-2 is essential for germ cell development in C. elegans and that this ubiquitous enzyme may play important roles in a tissue specific manner.

Amino Acid Sequence↗