Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to elucidate the reasons for the increased methionine-aminopeptidase activity in the rat cryptorchid testis, a histochemical study was conducted on the changes in testicular aminopeptidase activities using various substrates after the cryptorchidism experimentally was induced with reference to the regenerated hepatic cells which appeared in the partially hepatectomized liver of rat. Methionine-aminopeptidase gradually increased in Leydig cells after cryptorchid was induced, whereas the enzyme activity decreased in regenerated hepatic cells. These histochemical observations were coincident with the data obtained by enzyme assay. The present study has clearly indicated that the increased methionine aminopeptidase activity was specific for hyperplastic and hypertrophic Leydig cells in the cryptorchid testis, but did not depend merely on cell hyperplasia.
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PMID:Increase of methionine-aminopeptidase activity in hyperplastic Leydig cells of rat cryptorchid testis. 168 79

The selective distribution of methionyl aminopeptidase (MAP) among rat liver mitochondria (heavy and light) and microsomes is reported. Several properties of MAP from the three subcellular fractions showed that the enzyme is a typical aminopeptidase able to remove N-terminal methionine from oligopeptides and methionyl-2-naphthylamide but not from Met-Ala-Ser. MAP is a membrane-bound enzyme sensitive to SH-group oxidants and inhibitable by L-methionine but not by usual arylaminopeptidase inhibitors. It is suggested that, MAP may play an important role during protein synthesis in rat liver.
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PMID:Methionyl aminopeptidase from rat liver: distribution of the membrane-bound subcellular enzyme. 188 86

An aminopeptidase specific for methionine (peptidase M) has been purified from wild-type and mutant Salmonella typhimurium strains. Recombinant peptidase M was also purified from Escherichia coli. These preparations were characterized with respect to their physicochemical properties using analytical ultracentrifugation, SDS/PAGE, isoelectric focusing, titration curve analysis, amino acid analysis, N-and C-terminal sequencing and various spectroscopic methods. Peptidase M activity is stimulated by Co2+, in agreement with previous studies using crude extracts of Salmonella. The purified preparations did not contain significant amounts of any metal. Enzymically important metal is loosely associated and lost during enzyme purification. Peptidase M was shown to contain seven free sulphydryl residues none of which are involved in either intra-or inter-molecular disulphide bonds. Most appear solvent-accessible as evidenced by their reactivity under native conditions. Limited modification of the sulphydryl residues with either iodoacetamide or 5,5'-dithiobis(2-nitrobenzoic acid) led to inactivation. Several cysteines were shown to be labelled to various degrees by peptide mapping of inactivated S-[14C]carboxymethylated protein. Whether cysteine modification affects enzymic activity directly (blocking an active site) or indirectly (by causing conformational change) remains to be established.
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PMID:Purification and characterization of a methionine-specific aminopeptidase from Salmonella typhimurium. 265 Nov 23

Crude extracts of a multiply peptidase-deficient strain of Salmonella typhimurium contain an aminopeptidase that specifically removes N-terminal methionine from peptides. This activity shows pronounced specificity for the peptide's second amino acid. Methionine is removed from peptides with alanine, threonine, or glycine in this position but not when the second amino acid is leucine or methionine. The activity is stimulated by Co2+ and is inhibited by EDTA. Mutations that lead to overproduction (up to 30-fold) of the activity have been obtained by selecting for growth on Met-Gly-Gly as a methionine source. These mutations map at approximately 3 map units, phage P22 cotransducible with leu. The overproducer mutations are dominant to wild type, and duplication of the wild-type allele of the locus leads to a gene dosage effect on peptidase levels. This suggests that the locus of the overproducer mutations may be the structural gene for the peptidase. NaDodSO4/PAGE shows an increased level of a single protein (34 kDa) in the overproducer mutant. This protein is highly enriched in a purified preparation of the peptidase. The specificity of this enzyme suggests that it is involved in the cleavage of methionine from newly synthesized peptide chains. This activity can specifically remove methionine from the N terminus of a completed protein. Treatment of purified, unprocessed (N-terminal methionine) interleukin 1 beta with the purified peptidase results in removal of N-terminal methionine with no additional alterations. N-terminal processing of at least this protein can occur after translation is complete. We propose to call this enzyme peptidase M (methionine-specific aminopeptidase).
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PMID:N-terminal methionine-specific peptidase in Salmonella typhimurium. 310 76

A methionine aminopeptidase (MAP) found in rat liver microsomes behaves as membrane-bound enzyme. Triton-solubilized MAP when chromatographed on DEAE-cellulose columns was separated from other microsomal arylamidases. The enzyme hydrolyzes N-terminal methionine from methionyl-lysyl-bradykinin (Met-Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) being then characterized as a typical aminopeptidase. It also shows preferential arylamidase activity upon Met-2-naphthylamide. MAP was activated by 2-mercaptoethanol and inhibited by p-hydroxymercuribenzoate. Contrarily to other well characterized aminopeptidases, MAP was not affected by EDTA, puromycin or bestatin. Altogether these data suggest that MAP is a unique microsomal enzyme distinct from other previously described aminopeptidases. It could be involved in the removal of methionine from nascent peptides during protein synthesis.
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PMID:Microsomal methionine aminopeptidase: properties of the detergent-solubilized enzyme. 393 47

The structure of the proline-specific aminopeptidase (EC 3.4.11.9) from Escherichia coli has been solved and refined for crystals of the native enzyme at a 2.0-A resolution, for a dipeptide-inhibited complex at 2.3-A resolution, and for a low-pH inactive form at 2.7-A resolution. The protein crystallizes as a tetramer, more correctly a dimer of dimers, at both high and low pH, consistent with observations from analytical ultracentrifuge studies that show that the protein is a tetramer under physiological conditions. The monomer folds into two domains. The active site, in the larger C-terminal domain, contains a dinuclear manganese center in which a bridging water molecule or hydroxide ion appears poised to act as the nucleophile in the attack on the scissile peptide bond of Xaa-Pro. The metal-binding residues are located in a single subunit, but the residues surrounding the active site are contributed by three subunits. The fold of the protein resembles that of creatine amidinohydrolase (creatinase, not a metalloenzyme). The C-terminal catalytic domain is also similar to the single-domain enzyme methionine aminopeptidase that has a dinuclear cobalt center.
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PMID:Structure and mechanism of a proline-specific aminopeptidase from Escherichia coli. 952 Mar 90

Human soluble ("cytosolic") aminopeptidase P (hsAmP) is an aminoacylprolyl hydrolase (EC 3.4.11.9) present in all tissues yet examined. hsAmP is related in terms of catalytic specificity to an ectoenzyme, membrane aminopeptidase P (hmAmP), which is largely limited in distribution to endothelia and brush border epithelia. Although both enzymes can degrade oligopeptides having N-terminal Xaa-Pro- moieties, hsAmP and hmAmP are of relatively low sequence homology. Recently, it has been shown that the two enzymes are not products of splice variants of the same gene. How hsAmP relates to hmAmP has clinical significance in that both can inactivate bradykinin, and AmP deficiency states have been described. The hmAmP gene (XPNPEP2) is disposed at chromosome Xq25, a disposition with clear meaning in terms of inheritance of hmAmP deficiencies. To further explore similarities and differences between hsAmP and hmAmP, the present study was begun to determine the chromosomal disposition of the hsAmP gene. Here we show that the gene is sublocalized on chromosome 10q25.3. We also show that hsAmP and hmAmP contain homologous blocks of sequence common to members of the "pita bread-fold" protein family, of which Escherichia coli methionine aminopeptidase is the prototype. The prototype is known to contain a proton shuttle and five divalent metal ligands, counterparts of which we identify in the homologous blocks of sequence in both hsAmP and hmAmP and compare to E. coli aminopeptidase.
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PMID:Cloning, chromosomal sublocalization of the human soluble aminopeptidase P gene (XPNPEP1) to 10q25.3 and conservation of the putative proton shuttle and metal ligand binding sites with XPNPEP2. 1087 Oct 44

Streptomyces griseus aminopeptidase (SGAP) is a double-zinc exopeptidase with a high preference toward large hydrophobic amino-terminus residues. It is a monomer of a relatively low molecular weight (30 kDa), it is heat stable, it displays a high and efficient catalytic turnover, and its activity is modulated by calcium ions. The small size, high activity, and heat stability make SGAP a very attractive enzyme for various biotechnological applications, among which is the processing of recombinant DNA proteins and fusion protein products. Several free amino acids, such as phenylalanine, leucine, and methionine, were found to act as weak inhibitors of SGAP and hence were chosen for structural studies. These inhibitors can potentially be regarded as product analogs because one of the products obtained in a normal enzymatic reaction is the cleaved amino terminal amino acid of the substrate. The current study includes the X-ray crystallographic analysis of the SGAP complexes with methionine (1.53 A resolution), leucine (1.70 A resolution), and phenylalanine (1.80 A resolution). These three high-resolution structures have been used to fully characterize the SGAP active site and to identify some of the functional groups of the enzyme that are involved in enzyme-substrate and enzyme-product interactions. A unique binding site for the terminal amine group of the substrate (including the side chains of Glu131 and Asp160, as well as the carbonyl group of Arg202) is indicated to play an important role in the binding and orientation of both the substrate and the product of the catalytic reaction. These studies also suggest that Glu131 and Tyr246 are directly involved in the catalytic mechanism of the enzyme. Both of these residues seem to be important for substrate binding and orientation, as well as the stabilization of the tetrahedral transition state of the enzyme-substrate complex. Glu131 is specifically suggested to function as a general base during catalysis by promoting the nucleophilic attack of the zinc-bound water/hydroxide on the substrate carbonyl carbon. The structures of the three SGAP complexes are compared with recent structures of three related aminopeptidases: Aeromonas proteolytica aminopeptidase (AAP), leucine aminopeptidase (LAP), and methionine aminopeptidase (MAP) and their complexes with corresponding inhibitors and analogs. These structural results have been used for the simulation of several species along the reaction coordinate and for the suggestion of a general scheme for the proteolytic reaction catalyzed by SGAP.
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PMID:Interactions of Streptomyces griseus aminopeptidase with amino acid reaction products and their implications toward a catalytic mechanism. 1148 27

The aminopeptidase from Aeromonas proteolytica (AAP) was titrated with copper, which bound sequentially at two distinct sites. Both the mono- and disubstituted forms of AAP exhibited catalytic hyperactivity relative to the native dizinc enzyme. Monosubstituted AAP exhibited an axial Cu(II) EPR spectrum with slight pH dependence: at pH 6.0 g(parallel) = 2.249, g( perpendicular ) = 2.055, and A(parallel)((63/65)Cu) = 1.77 x 10(-)(2) cm(-)(1), whereas at pH 9.65 g(parallel) = 2.245, g( perpendicular ) = 2.056, and A(parallel)((63/65)Cu) = 1.77 x 10(-)(2) cm(-)(1). These data indicate oxygen and nitrogen ligation of Cu. AAP further substituted with copper exhibited a complex signal with features around g approximately 2 and 4. The features at g approximately 4 were relatively weak in the B(0) perpendicular B(1) (perpendicular) mode EPR spectrum but were intense in the B(0) parallel B(1) (parallel) mode spectrum. The g approximately 2 region of the perpendicular mode spectrum exhibited two components, one corresponding to mononuclear Cu(II) with g(parallel) = 2.218, g( perpendicular ) = 2.023, and A(parallel)((63/65)Cu) = 1.55 x 10(-)(2) cm(-)(1) and likely due to adventitious binding of Cu(II) to a site distant from the active site. Excellent simulations were obtained for the second component of the spectrum assuming that two Cu(II) ions experience dipolar coupling corresponding to an inter-copper distance of 5 A with the two Cu(II) g(z)() directions parallel to each other and at an angle of approximately 17 degrees to the inter-copper vector (H = betaB.g(CuA).S(CuA) + betaB.g(CuB).S(CuB) + [S.A.I](CuA) + [S.A.I](CuB) + [S(CuA).J.S(CuB)]; g(parallel(CuA,CuB)) = 2.218, g( perpendicular )((CuA,CuB)) = 2.060; A(parallel(CuA,CuB))((63/65)Cu) = 1.59 x 10(-)(2) cm(-)(1), J(isotropic) = 50 cm(-)(1), r(Cu)(-)(Cu) = 4.93 A, and chi = 17 degrees ). The exchange coupling between the two copper ions was found to be ferromagnetic as the signals exhibited Curie law temperature dependence. The Cu-Cu distance of approximately 5 A indicated by EPR was significantly higher than the inter-zinc distance of 3.5 A in the native enzyme, and the dicopper species therefore represents a novel dinuclear site capable of catalysis of hydrolysis. In contrast to AAP, the related methionyl aminopeptidase from Escherichia coli (EcMetAP) was found to bind only one Cu(II) ion despite possessing a dinuclear binding site motif. A further difference was the marked pH dependence of the signal in EcMetAP, suggestive of a change in ligation. The structural motifs of these two Cu(II)-substituted aminopeptidases provide important insight into the observed catalytic activity.
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PMID:Structurally distinct active sites in the copper(II)-substituted aminopeptidases from Aeromonas proteolytica and Escherichia coli. 1240 29

Fumagillin is a potent anti-angiogenic drug used in cancer treatments. It is also one of the few molecules active against the Enterocytozoon and Encephalitozoon parasites responsible for various clinical syndromes in HIV-infected or immunosuppressive treated patients. Its toxicity, however, makes desirable the design of more specific molecules. The fumagillin target, as anti-angiogenic agent, is the methionine aminopeptidase, an ubiquitous metallo-enzyme responsible for the removing of the N-terminal methionine in nascent proteins. By analogy, it has been proposed that this enzyme could also be the target in the parasites. As a first approach to verify this and to determine if it would be possible to design a more specific derivative, we have built a homology model of the E. cuniculi aminopeptidase. The charges of the two cobalt ions present in the active site and of the side-chains involved in their binding were computed using ab-initio methods. A preliminary comparison of the interactions of the fumagillin and of a related compound, the TNP-470, with both the human and the parasitic enzymes strongly support the hypothesis that the parasitic aminopeptidase is indeed the target of the fumagillin. It also suggests that the TNP-470 interact identically with both enzymes while there could be small differences in case of the fumagillin.
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PMID:Homology modeling and calculation of the cobalt cluster charges of the Encephazlitozoon cuniculi methionine aminopeptidase, a potential target for drug design. 1293 77


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