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A new enzyme: long acyl aminoacylase from Pseudomonas diminuta.

A new enzyme which hydrolyzes N-long chain acyl glutamic acid was found in cell-free extracts of Pseudomonas diminuta. Two active fractions (long acyl aminoacylase I and II) were separated by DEAE-cellulose column chromatography. The long acyl aminoacylase I was purified about 650-fold, and the purified preparation was electrophoretically homogeneous. The molecular weight was estimated to be 300,000 by gel filtration. The enzyme was unique in its substrate specificity. It hydrolyzed only N-long acyl glutamic acid and could not react with other N-acyl amino acids. Lauroyl (C12)-, myristoyl (C14)-, and palmitoyl (C16)- glutamic acid were good substrates, but acetyl glutamic acid was not hydrolyzed. Therefore this enzyme is considered to be a new acylase which is specific for N-long chain acyl glutamic acid, and it is designated as N-long acyl glutamic acid amidohydrolase [EC 3.5.1 group].

Amidohydrolases↗

Microbacterium natoriense sp. nov., a novel D-aminoacylase-producing bacterium isolated from soil in Natori, Japan.

A rod-shaped, Gram-positive bacterium, strain TNJL143-2(T), having N-acyl-D-amino acid amidohydrolase (D-aminoacylase) activity, was isolated from a soil sample from Natori, Japan. It was a non-spore-forming, strictly aerobic bacterium without motility, showing a temperature optimum for growth of 30 degrees C and a pH optimum for growth of 5-7. The 16S rRNA gene sequence of the strain showed the highest similarities to members of the genus Microbacterium, in particular, Microbacterium aerolatum, Microbacterium foliorum and Microbacterium phyllosphaerae. The chemotaxonomic characteristics, including the compositions of cellular menaquinones, cellular fatty acids and cell-wall amino acids, were consistent with those described for the genus Microbacterium. The G+C content of the genomic DNA was determined as 69.1 mol%. DNA-DNA hybridization studies using type strains of M. aerolatum, M. foliorum and M. phyllosphaerae showed only low levels of relatedness (11-12 %). On the basis of these phenotypic and genotypic results, a novel species, Microbacterium natoriense sp. nov., is proposed, with TNJL143-2(T) (=JCM 12611(T)=ATCC BAA-1032(T)) as the type strain.

Actinomycetales↗

Immunoaffinity purification and comparison of allantoinases from soybean root nodules and cotyledons.

Allantoinase (allantoin amidohydrolase, EC 3.5.2.5) catalyzes the conversion of allantoin to allantoic acid in the final step of ureide biogenesis. We have purified allantoinase more than 4000-fold by immunoaffinity chromatography from root nodules and cotyledons of soybean (Glycine max [L] Merr.). We characterized and compared properties of the enzyme from the two sources. Seed and nodule allantoinases had 80% identity in the first 24 amino acid residues of the N terminus. Two-dimensional gel electrophoresis of the purified enzymes showed that multiple forms were present in each. Allantoinases from nodules and cotyledons had very low affinity for allantoin with a Km for allantoin of 17.3 mM in cotyledons and 24.4 mM in nodules. Both had activity in a broad range of pH values from 6.5 to 7.5. In addition, purified allantoinase from both sources was very heat stable. Enzyme activity was stable after 1 h at 70 degrees C, decreased gradually with heating to 85 degrees C, and was lost at 90 to 95 degrees C. Although these studies have revealed some differences between allantoinases in seeds and nodules, the differences were not reflected in key enzyme properties. The immunoaffinity approach enabled purification of allantoinase from soybean root nodules and simplified its purification from cotyledons, thereby allowing characterization and comparison of the enzyme from the two sources.

Amidohydrolases↗

Characterization of plant beta-ureidopropionase and functional overexpression in Escherichia coli.

Pyrimidine bases are rapidly catabolized in growing plant tissues. The final enzyme of the catabolic pathway, beta-ureidopropionase (beta-UP; EC 3.5.1.6), was partially purified from the shoots of etiolated maize (Zea mays) seedlings. The enzyme had a K(m) for beta-ureidopropionate (the substrate derived from uracil) of 11 microM. Only one enantiomer of racemic beta-ureidoisobutyrate (derived from thymine) was processed with a K(m) of 6 microM. The enzyme was inactivated by dialysis against 1,10-phenanthroline and activity could be partially restored by addition of Zn(2+). Maize beta-UP was very sensitive to inactivation by iodoacetamide. This could be prevented by addition of substrate, indicating the presence of an active site Cys. The enzyme was strongly inhibited by short chain aliphatic acids and aryl propionates, the most potent inhibitor of which was 2-(2, 6-dinitrophenoxy)-propionate (I(50) = 0.5 microM). A gene for Arabidopsis beta-UP encodes a polypeptide of 405 amino acids and has about 55% homology with the enzymes from other eukaryotic organisms. Several highly conserved residues link the plant beta-UP with a larger class of prokaryotic and eukaryotic amidohydrolases. An Arabidopsis cDNA truncated at the N terminus by 14 residues was cloned and overexpressed in Escherichia coli. The recombinant enzyme (43.7 kD) was soluble, functional, and purified to homogeneity with yields of 15 to 20 mg per 30 g fresh weight of E. coli cells. The recombinant enzyme from Arabidopsis and the native enzyme from maize had molecular masses of approximately 440 kD, indicating the enzyme is a decamer at pH 7.

Amidohydrolases↗

Crystallization and preliminary crystallographic analysis of a D-aminoacylase from Alcaligenes faecalis DA1.

D-Aminoacylases catalyze the hydrolysis of N-acyl-D-amino acids into D-amino acids with the aid of zinc ions. The first D-aminoacylase crystal from Alcaligenes faecalis has been obtained in hanging drops at pH 5.6 by the vapour-diffusion method using 30% polyethylene glycol 4000 as precipitant. It belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 60.2, b = 76.6, c = 135.3 A. Reflections to 1.2 A resolution are observable. An initial atomic model with 472 residues has been built based on SeMet SAD data at 1.8 A resolution. Unexpectedly, the structure revealed a novel metal centre in the amidohydrolase superfamily.

Alcaligenes↗

Crystallization and preliminary X-ray diffraction analysis of thermophilic imidase from pig liver.

Imidase is an enzyme, also known as dihydropyrimidinase (EC 3.5.2.2), hydantoinase, dihydropyrimidine hydrase or dihydropyrimidine amidohydrolase, that catalyzes the reversible hydrolysis of 5,6-dihydrouracil to 3-ureidopropionate and many other imides. Substrate specificity, metal content and amino-acid sequence all differ significantly between bacterial and mammalian imide-hydrolyzing enzymes. In this study, a thermophilic imidase was isolated from pig liver and crystallized. Two kinds of imidase crystals were grown by the hanging-drop vapour-diffusion method using polyethylene glycol MME 5000 and 2-propanol as precipitants. One belongs to the triclinic P(1) space group, with unit-cell parameters a = 96.35, b = 96.87, c = 154.87 A, alpha = 82.10, beta = 72.54, gamma = 77.19 degrees, and the other belongs to the orthorhombic C222(1) space group, with unit-cell parameters a = 113.92, b = 157.22, c = 156.21 A.

Amidohydrolases↗

Structural-based mutational analysis of D-aminoacylase from Alcaligenes faecalis DA1.

D-Aminoacylase is an attractive candidate for commercial production of D-amino acids through its catalysis in the zinc-assistant hydrolysis of N-acyl-D-amino acids. We report here the cloning, expression, and structural-based mutation of the D-aminoacylase from Alcaligenes faecalis DA1. A 1,007-bp PCR product amplified with degenerate primers, was used to isolate a 4-kb genomic fragment, encoding a 484-residue D-aminoacylase. The enzyme amino-terminal segment shared significant homology within a variety of enzymes including urease. The structural fold was predicted by 3D-PSSM to be similar to urease and dihydroorotase, which have grouped into a novel alpha/beta-barrel amidohydrolase superfamily with a virtually indistinguishable binuclear metal centers containing six ligands, four histidines, one aspartate, and one carboxylated lysine. Three histidines, His-67, His-69, and His-250, putative metal ligands in D-aminoacylase, have been mutated previously, the remaining histidine (His-220) and aspartate (Asp-366) Asp-65, and four cysteines were then characterized. Substitution of Asp-65, Cys-96, His-220, and Asp-366 with alanine abolished the enzyme activity. The H220A mutant bound approximately half the normal complement of zinc ion as did H250N. However, the C96A mutant showed little zinc-binding ability, revealing that Cys-96 may replace the carboxylated lysine to serve as a bridging ligand. According to the urease structure, the conserved amino-terminal segment including Asp-65 may be responsible for structural stabilization.

Alcaligenes↗

Identification and characterization of an aliphatic amidase in Helicobacter pylori.

We report, for the first time, the presence in Helicobacter pylori of an aliphatic amidase that, like urease, contributes to ammonia production. Aliphatic amidases are cytoplasmic acylamide amidohydrolases (EC 3.5.1.4) hydrolysing short-chain aliphatic amides to produce ammonia and the corresponding organic acid. The finding of an aliphatic amidase in H. pylori was unexpected as this enzyme has only previously been described in bacteria of environmental (soil or water) origin. The H. pylori amidase gene amiE (1017 bp) was sequenced, and the deduced amino acid sequence of AmiE (37746Da) is very similar (75% identity) to the other two sequenced aliphatic amidases, one from Pseudomonas aeruginosa and one from Rhodococcus sp. R312. Amidase activity was measured as the release of ammonia by sonicated crude extracts from H. pylori strains and from recombinant Escherichia coli strains overproducing the H. pylori amidase. The substrate specificity was analysed with crude extracts from H. pylori cells grown in vitro; the best substrates were propionamide, acrylamide and acetamide. Polymerase chain reaction (PCR) amplification of an internal amiE sequence was obtained with each of 45 different H. pylori clinical isolates, suggesting that amidase is common to all H. pylori strains. A H. pylori mutant (N6-836) carrying an interrupted amiE gene was constructed by allelic exchange. No amidase activity could be detected in N6-836. In a N6-urease negative mutant, amidase activity was two- to threefold higher than in the parental strain N6. Crude extracts of strain N6 slowly hydrolysed formamide. This activity was affected in neither the amidase negative strain (N6-836) nor a double mutant strain deficient in both amidase and urease activities, suggesting the presence of an independent discrete formamidase in H. pylori. The existence of an aliphatic amidase, a correlation between the urease and amidase activities and the possible presence of a formamidase indicates that H. pylori has a large range of possibilities for intracellular ammonia production.

Amidohydrolases↗

The T-region of Ti plasmids codes for an enzyme synthesizing indole-3-acetic acid.

Gene 2 from the T region of Ti plasmids appears to be expressed both in eucaryotic and in procaryotic systems. In transformed plant cells it participates in auxin-controlled growth and differentiation, and in bacteria it is expressed into a defined protein of Mr 49000. We investigated the possibility that it codes for an enzyme involved in auxin biosynthesis. Only extracts from Escherichia coli cells expressing gene 2 hydrolyzed indole-3-acetamide into a substance which was unambiguously identified as indole-3-acetic acid. The same reaction was found in Agrobacteria containing gene 2, but not in strains lacking the gene. Extracts from tobacco crown gall cells, but not from non-transformed cells, showed the same enzyme activity, and the reaction product was also identified as indole-3-acetic acid. The results indicate that gene 2 of the T region, which participates in tumorous growth of plant cells, codes both in bacteria and in plants for an amidohydrolase involved in the biosynthesis of the plant hormone indole-3-acetic acid.

Amidohydrolases↗

Purification and characterization of N,N-dimethylformamidase from Pseudomonas DMF 3/3.

The N,N-dimethylformamide-hydrolyzing enzyme (DMFase) from Pseudomonas DMF 3/3 has been purified to apparent electrophoretic homogeneity with an overall 49-fold purification, a 24% yield and a final specific activity of 1.98 mumol N,N-dimethylformamide (DMF) hydrolyzed min-1 (mg protein)-1. The native DMFase has a relative molecular mass of 250 000 and is composed of two light-chain (Mr = 15 000) and two heavy-chain (Mr = 105 000) subunits. The stability of DMFase is optimal at pH values above 7.5 and at temperatures below 20 degrees C. The activity of the enzyme is inhibited by metal-chelating agents such as EDTA and 2,2'-dipyridyl. Emission and atomic absorption spectroscopy measurements showed that iron is present in significant amounts in DMFase, indicating that it is an iron-containing amidohydrolase. In the ultraviolet/visible spectrum prominent bands were observed at 224 nm, 280 nm and 396 nm and shoulders are present at 418 nm and 467 nm. DMFase from Ps. DMF 3/3 has an isoelectric point of 7.7. The enzyme exhibits optimal activity between pH 5 and 6 and at 40 degrees C. The substrate spectrum is rather narrow. The enzyme hydrolyzes preferentially substituted short-chain aliphatic amides such as DMF, N-ethylformamide and N-methylformamide. N,N-dimethylformamide, N,N-dimethylacetamide and unsubstituted amides, e.g. formamide, prolinamide, acetamide, acrylamide and butyramide are substrates as well, but are hydrolysed at significantly lower rates. DMFase obeys Michaelis-Menten kinetics and its Km and Vmax values for DMF are 13.8 mM and 1.89 U/mg, respectively, as determined from a Lineweaver-Burk plot.

Amidohydrolases↗

Catalysis by hog-kidney aminoacylase does not involve a covalent intermediate.

Hog kidney aminoacylase (N-acylamino acid amidohydrolase; acylase I) is shown to catalyze the exchange of acetate oxygens with water at a significant rate only when alanine is present simultaneously. These studies, conducted using the 18O-isotope induced shift on 13C-NMR spectra, provide evidence in favor of a linear kinetic mechanism as opposed to a 'ping-pong' double-displacement mechanism. At pH values above neutrality, aminoacylase I also catalyzes the exchange of alanine oxygens with those of water. Ionic strength and pH effects on the kinetics of aminoacylase I are examined and the results are interpreted in terms of a model of the enzyme active site.

Acetates↗

A family of auxin conjugate hydrolases from Brassica rapa: characterization and expression during clubroot disease.

During the obligate biotrophic interaction of Plasmodiophora brassicae with members of the Brassicaceae, the host roots show hypertrophy and galls are established. An increased auxin pool appears to correlate with cell expansion and cell division, but the origin of the free auxin is not yet clear. As previous results point to increased IAA-hydrolytic activity in infected roots of Brassica rapa at later time points of infection, we isolated IAA-amidohydrolase-like genes from various tissues. We cloned full-length cDNAs of two genes with high homology to the Arabidopsis IAR3 (Br-IAR3) as well as full-length clones corresponding to the Arabidopsis ILL2/ILL1 (Br-ILL2) and ILL6 (Br-ILL6) hydrolase genes. Using heterologous expression in Escherichia coli, we showed that Br-IAR3 24 and Br-ILL2 possess hydrolytic activity in vitro. Real-time reverse transcription (RT)-PCR revealed that only Br-IAR3 25 and Br-ILL6 are expressed differentially during clubroot disease, but showed a decreased expression at later time point of infection. These findings are discussed with regard to a negative regulation in IAA homeostasis during clubroot disease.

Actins↗

Purification, characterization, and localization of aspartoacylase from bovine brain.

Canavan disease, an autosomal recessive disorder, is characterized biochemically by N-acetylaspartic aciduria and aspartoacylase (N-acyl-L-aspartate amidohydrolase; EC 3.5.1.15) deficiency. However, the role of aspartoacylase and N-acetylaspartic acid in brain metabolism is unknown. Aspartoacylase has been purified to apparent homogeneity with a specific activity of approximately 19,000-20,000 nmol of aspartate released/mg of protein. The native enzyme is a 58-kDa monomer. The purified aspartoacylase activity is enhanced by divalent cations, nonionic detergents, and dithiothreitol. Low levels of dithiothreitol or beta-mercaptoethanol are required for enzyme stability. Aspartoacylase has a Km of 8.5 x 10(-4) M and a Vmax of 43,000 nmol/min/mg of protein. Inhibition of aspartoacylase by glycyl-L-aspartate and amino derivatives of D-aspartic acid suggests that the carbon backbone of the substrate is primarily involved in its interaction with the active site and that a blocked amino group is essential for the catalytic activity of aspartoacylase. Biochemical and immunocytochemical studies revealed that aspartoacylase is localized to white matter, whereas the N-acetylaspartic acid concentration is threefold higher in gray matter than in white matter. Our studies so far indicate that aspartoacylase is conserved across species during evolution and suggest a significant role for aspartoacylase and N-acetylaspartic acid in normal brain biology.

Amidohydrolases↗

A cyclooxygenase metabolite of anandamide causes inhibition of interleukin-2 secretion in murine splenocytes.

Arachidonyl ethanolamine, which is commonly known as anandamide, was the first endogenous compound to be identified that binds to the cannabinoid receptors. Anandamide mimics many of the physiological effects of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), including hypothermia, antinociception, immobility, catalepsy, and immune modulation. In the present studies, we show that anandamide caused a concentration-dependent inhibition of interleukin-2 in primary splenocytes. The CB1 and CB2 antagonists, SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorphenyl)-4-methyl-H-pyrazole-3 carboxyamidehydrochloride] and SR144528 [N-[(1S)-endo-1,3,3,-trimethylbicyclo[2,2,1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide], when used in combination, did not antagonize the inhibition of interleukin-2 by anandamide. Additionally, neither UCM707 [N-(3-furanylmethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide], the inhibitor of the putative anandamide membrane transporter (AMT), nor methyl arachidonoyl fluorophosphonate (MAFP), the inhibitor of fatty acid amidohydrolase (FAAH), were able to affect the inhibitory activity of anandamide upon interleukin-2. Interestingly, arachidonic acid caused a concentration-dependent inhibition of interleukin-2 secretion (IC(50) = 10.3 microM), which was similar to that of structurally related anandamide (IC(50) = 11.4 microM). The inhibition of interleukin-2 by anandamide and arachidonic acid was partially reversed by pretreatment with the nonspecific cyclooxygenase inhibitors, flurbiprofen and piroxicam. Moreover, NS398 [N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide], a cyclooxygenase-2-specific inhibitor, also attenuated the inhibitory effects of anandamide and arachidonic acid upon interleukin-2 secretion. Finally, pretreatment with a peroxisome proliferator-activated receptor gamma (PPARgamma)-specific antagonist, T0070907 [2-chloro-5-nitro-N-4-pyridinyl-benzamide], partially antagonized anandamide-mediated suppression of IL-2 secretion. Collectively, the aforementioned studies suggest that inhibition of interleukin-2 secretion by anandamide is independent of CB1/CB2 and the AMT/FAAH system. Additionally, these studies also suggest that inhibition of interleukin-2 is mediated by a PPARgamma, which is activated by a cyclooxygenase-2 metabolite of anandamide.

Amidohydrolases↗

Human platelets and polymorphonuclear leukocytes synthesize oxygenated derivatives of arachidonylethanolamide (anandamide): their affinities for cannabinoid receptors and pathways of inactivation.

Arachidonylethanolamide (AEA), the putative endogenous ligand of the cannabinoid receptor, has been shown to be a substrate for lipoxygenase enzymes in vitro. One goal of this study was to determine whether lipoxygenase-rich cells metabolize AEA. [14C]AEA was converted by human polymorphonuclear leukocytes (PMNs) to two major metabolites that comigrated with synthetic 12(S)- and 15(S)-hydroxy-arachidonylethanolamide (HAEA). Human platelets convert [14C]AEA to 12(S)-HAEA. 12(S)-HAEA binds to both CB1 and CB2 receptors with approximately the same affinity as AEA. 12(R)-HAEA, which is not produced by PMNs, has 2-fold lower affinity for the CB1 receptor and 10-fold lower affinity for the CB2 receptor than 12(S)-HAEA. 15-HAEA has a lower affinity than AEA for both receptors, with Ki values of 738 and >1000 nM for CB1 and CB2 receptors, respectively. The addition of a hydroxyl group at C20 of AEA resulted in a ligand with the same affinity for the CB1 receptor but a 4-fold lower affinity for the CB2 receptor than AEA. 12(S)-HAEA and 15-HAEA are poor substrates for AEA amidohydrolase and do not bind to the AEA uptake carrier. In conclusion, the addition of a hydroxyl group at C12 of the arachidonate backbone of AEA does not affect binding to CB receptors but is likely to increase its half-life. The addition of hydroxyl groups at other positions affects ligand affinity for CB receptors; both the position of the hydroxyl group and the configuration of the remaining double bonds are determinants of affinity.

Amidohydrolases↗

Cloning, sequencing, and expression in Escherichia coli of the D-hydantoinase gene from Pseudomonas putida and distribution of homologous genes in other microorganisms.

Pseudomonas putida DSM 84 produces N-carbamyl-D-amino acids from the corresponding D-5-monosubstituted hydantoins. The gene encoding this D-hydantoinase enzyme was cloned and expressed in Escherichia coli. The nucleotide sequence of the 1.8-kb insert of subclone pGES19 was determined. One open reading frame of 1,104 bp was found and was predicted to encode a polypeptide with a molecular size of 40.5 kDa. Local regions of identity between the predicted amino acid sequence and that of other known amidohydrolases (two other D-hydantoinases, allantionase and dihydroorotase) were found. The D-hydantoinase gene was used as a probe to screen DNA isolated from diverse organisms. Within Pseudomonas strains of rRNA group I, the probe was specific. The probe did not detect D-hydantoinase genes in pseudomonads not in rRNA group I, other bacteria, or plants known to express D-hydantoinase activity.

Amidohydrolases↗

Biochemical decomposition of the herbicide N-(3,4-dichlorophenyl)-2-methylpentanamide and related compounds.

Organisms capable of decomposing N-(3,4-dichlorophenyl)-2-methylpentanamide (Karsil) were isolated, identified, and tested for their ability to hydrolyze this herbicide. Primary products of Karsil decomposition by cells and cell-free extracts of a Penicillium sp. were identified as 2-methyl-valeric acid and 3,4-dichloroaniline. The Karsil acylamidase (EC 3.5.1.a aryl acylamine amidohydrolase) was an induced enzyme. It was partially purified and tested for its ability to hydrolyze 25 related compounds. Some relations between the structures of these compounds and their susceptibility to enzymatic hydrolysis were discerned.

Amidohydrolases↗

Herbicide transformation. II. Studies with an acylamidase of Fusarium solani.

Replacement cultures liberated 3,4-dichloroaniline (DCA) from 3,4-dichloropropionanilide (propanil). The kinetics of the conversion suggest a requirement for de novo enzyme synthesis, but the system was not influenced by chloramphenicol or puromycin. Enzyme activity was detected when acetanilide (K(m) = 0.195 mm) was used to replace propanil as substrate. Fungal acylamidase (E.C. 3.5.1., an aryl acylamine amidohydrolase) was concentrated by salt precipitation and characterized. The Fusarium solani acylamidase exhibited an optimum at pH 7.5 to 9.0 and was inactivated in 10 min at 50 C. The enzyme was not sensitive to methyl-carbamate or organophosphate insecticides, but the herbicide, Ramrod (N-isopropyl-2-chloroacetanilide), acted as a competitive inhibitor of acetanilide hydrolysis (K(i) = 0.167 mm). Hydrolysis rates were decreased by various para substitutions of acetanilide. Chloro substitution in the acyl moiety of acetanilide also reduced the rate of hydrolysis. 3,4-Dichloroacetanilide was less susceptible to enzyme action than acetanilide, but 3,4-dichloropropionanilide was hydrolyzed much more rapidly than propionanilide. The fungal acylamidase was highly specific for N-acetylarylamines. It did not catalyze hydrolysis of formanilide, butyranilide, dicryl, Karsil, fenuron, monuron, or isopropyl-N-phenylcarbamate. It appears to differ from acylamidases that have been isolated from rice, rat liver, chick kidney, and Neurospora.

Acetanilides↗