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PubMed1998

Overexpression of high-molecular-mass nitrile hydratase from Rhodococcus rhodochrous J1 in recombinant Rhodococcus cells.

High-molecular-mass nitrile hydratase (H-NHase, 530 kDa) is a cobalt-containing enzyme produced by Rhodococcus rhodochrous J1. For efficient production of H-NHase in R. rhodochrous ATCC12674, several plasmids were constructed. The enzyme was produced in the recombinant Rhodococcus cells only in the presence of an upstream region (approximately 4 kb) of the H-NHase gene under the control of the promoter for the amidase-NHase gene cluster from Rhodococcus sp. N-774. Although H-NHase was produced as a soluble protein in the cells, the protein did not show NHase activity. However, when the recombinant R. rhodochrous ATCC12674 cells were cultured in the presence of amide compounds, such as crotonamide and methacrylamide, markedly high NHase activity was detected, Gel-filtration chromatography revealed that the NHases produced by the cells grown in the presence and absence of the amide compounds had a molecular mass of more than 500 kDa and 50-80 kDa respectively. These results suggest that the amide compounds are essential for subunit assembly to form an enzymatically active multimer. By the use of the recombinant expression system, NHase activity 1.7 times higher than that of the original strain, R. rhodochrous J1, was achieved.

Dose-Response Relationship, Drug↗

PubMed2001

Physiological characterisation of Penicillium chrysogenum strains expressing the expandase gene from Streptomyces clavuligerus during batch cultivations. Growth and adipoyl-7-aminodeacetoxycephalosporanic acid production.

The production of adipoyl-7-aminodeacetoxy-cephalosporanic acid (ad-7-ADCA) was studied, using two recombinant strains of Penicillium chrysogenum carrying the expandase gene from Streptomyces clavuligerus. The adipoyl-side chain of this compound may easily be removed using an amidase; and this process therefore represents a new route for the production of 7-ADCA, which serves as a precursor for the production of many semi-synthetic cephalosporins. In this study, one low- and one high-yielding strains were characterised and the specific productivities of ad-7-ADCA and byproducts of the biosynthetic pathway were compared. The fluxes through the biosynthetic pathway were quantified and it was found that there was a 30% higher flux through the expandase in the high-yielding strain. In both strains, there was a significant degradation of adipate. Furthermore, the initial adipate concentration in batch cultures was shown to have a positive effect on the formation of ad-7-ADCA.

Adipates↗

PubMed1998

Biochemistry and biotechnology of mesophilic and thermophilic nitrile metabolizing enzymes.

Mesophilic nitrile-degrading enzymes are widely dispersed in the Bacteria and lower orders of the eukaryotic kingdom. Two distinct enzyme systems, a nitrilase catalyzing the direct conversion of nitriles to carboxylic acids and separate but cotranscribed nitrile hydratase and amidase activities, are now well known. Nitrile hydratases are metalloenzymes, incorporating FeIII or CoII ions in thiolate ligand networks where they function as Lewis acids. In comparison, nitrilases are thiol-enzymes and the two enzyme groups have little or no apparent sequence or structural homology. The hydratases typically exist as alpha beta dimers or tetramers in which the alpha- and beta-subunits are similar in size but otherwise unrelated. Nitrilases however, are usually found as homomultimers with as many as 16 subunits. Until recently, the two nitrile-degrading enzyme classes were clearly separated by functional differences, the nitrile hydratases being aliphatic substrate specific and lacking stereoselectivity, whereas the nitrilases are enantioselective and aromatic substrate specific. The recent discovery of novel enzymes in both classes (including thermophilic representatives) has blurred these functional distinctions. Purified mesophilic nitrile-degrading enzymes are typically thermolabile in buffered solution, rarely withstanding exposure to temperatures above 50 degrees C without rapid inactivation. However, operational thermostability is often increased by addition of aliphatic acids or by use of immobilized whole cells. Low molecular stability has frequently been cited as a reason for the limited industrial application of "nitrilases"; such statements notwithstanding, these enzymes have been successfully applied for more than a decade to the kiloton production of acrylamide and more recently to the smaller-scale production of nicotinic acid, R-(-)-mandelic acid and S-(+)-ibuprofen. There is also a rapidly growing catalog of other potentially useful conversions of complex nitriles in which the regioselectivity of the enzyme coupled with the ability to achieve high conversion efficiencies without detriment to other sensitive functionalities is a distinct process advantage.

Acrylamide↗

PubMed2006

Transformation of the herbicide 2,6-dichlorobenzonitrile to the persistent metabolite 2,6-dichlorobenzamide (BAM) by soil bacteria known to harbour nitrile hydratase or nitrilase.

In soil the herbicide 2,6-dichlorobenzonitrile (dichlobenil) is degraded to the persistent metabolite 2,6-dichlorobenzamide (BAM) which has been detected in 19% of samples taken from Danish groundwater. We tested if common soil bacteria harbouring nitrile-degrading enzymes, nitrile hydratases or nitrilases, were able to degrade dichlobenil in vitro. We showed that several strains degraded dichlobenil stoichiometrically to BAM in 1.5-6.0 days; formation of the amide intermediate thus showed nitrile hydratase rather than nitrilase activity, which would result in formation of 2,6-dichlorobenzoic acid. The non-halogenated analogue benzonitrile was also degraded, but here the benzamide intermediate accumulated only transiently showing nitrile hydratase followed by amidase activity. We conclude that a potential for dichlobenil degradation to BAM is found commonly in soil bacteria, whereas further degradation of the BAM intermediate could not be demonstrated.

Aminohydrolases↗

PubMed2006

Structural characterization of the N-glycans of gpMuc from Mucuna pruriens seeds.

Mucuna pruriens seeds are used in some countries as a human prophylactic oral anti-snake remedy. Aqueous extracts of M. pruriens seeds possess in vivo activity against cobra and viper venoms, and protect mice against Echis carinatus venom. It was recently demonstrated that the seed immunogen generating the antibody that cross-reacts with the venom proteins is a multiform glycoprotein (gpMuc), and the immunogenic properties of gpMuc seemed to mainly reside in its glycan chains. In the present study, gpMuc was found to contain only N-glycans. Part of the N-glycans could be released with peptide-(N (4)-(N-acetyl-beta -glucosaminyl)asparagine amidase F (PNGase F-sensitive N-glycans); the PNGase F-resistant N-glycans were PNGase A-sensitive. The oligosaccharides released were analyzed by a combination of MALDI-TOF mass spectrometry, HPLC profiling of 2-aminobenzamide-labelled derivatives and (1)H NMR spectroscopy. The PNGase F-sensitive N-glycans comprised a mixture of oligomannose-type structures ranging from Man(5)GlcNAc(2) to Man(9)GlcNAc(2), and two xylosylated structures, Xyl(1)Man(3)GlcNAc(2) and Xyl(1)Man(4)GlcNAc(2). The PNGase A-sensitive N-glycans, containing (alpha 1-3)-linked fucose, were identified as Fuc(1)Xyl(1)Man(2)GlcNAc(2) and Fuc(1)Xyl(1)Man(3)GlcNAc(2). In view of the determined N-glycan ensemble, the immunoreactivity of gpMuc was ascribed to the presence of core (beta 1-2)-linked xylose- and core alpha (1-3)-linked fucose-modified N-glycan chains.

Animals↗

PubMed1987

Use of N-glycanase to release asparagine-linked oligosaccharides for structural analysis.

An enzymatic procedure for releasing asparagine-linked oligosaccharides from glycoproteins by treatment with N-glycanase (peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase) has been investigated. Ribonuclease B, transferrin, fetuin, and alpha 1-acid glycoprotein were treated with N-glycanase and the released oligosaccharides were radiolabeled with NaB3H4. Lectin staining of the N-glycanase-treated proteins indicated that the deglycosylation reactions had proceeded to completion. The labeled carbohydrate chains were analyzed by HPLC on Micro-Pak AX-5 and AX-10 columns. The proportion of high-mannose and bi-, tri-, and tetraantennary complex chains obtained from each glycoprotein was in agreement with literature values. These results demonstrate that N-glycanase provides a simple method to release all common classes of asparagine-linked oligosaccharides from a glycoprotein in a form that can be radiolabeled directly for structural analysis.

Borohydrides↗

PubMed1990

Isolation and separation of the glycan strands from murein of Escherichia coli by reversed-phase high-performance liquid chromatography.

The length distribution of the glycan strands in the murein (peptidoglycan) sacculus of Escherichia coli has been analyzed after solubilization of the murein by complete digestion with human serum amidase. The glycan strands released were separated according to length by reversed-phase HPLC on wide-pore Nucleosil 300 C18 material at 50 degrees C, employing a convex gradient from 5 to 11% acetonitrile. The length of the fractionated glycan strands, which carry a nonreducing 1,6-anhydromuramic acid as a natural end group, was calculated from the ratio of total to nonreducing terminal muramic acid residues. This was possible after complete hydrolysis of the isolated glycan strands by muramidase followed by separation of the released nonreducing and reducing di- and tetrasaccharides by reversed-phase HPLC on Hypersil C18. The method established allows the separation of the glycan strands of murein, a poly-GlcNAc(beta 1-4)MurNAc-polysaccharide, up to a degree of polymerization of approximately 60. The predominant lengths of the glycan strands were 5 to 10 GlcNAc(beta 1-4)MurNAc disaccharide units.

Acetylglucosamine↗

PubMed1983

Kinetic studies on the chymotrypsin A alpha-catalyzed hydrolysis of a series of N-acetyl-L-phenylalanyl peptides.

A series of N-acetyl-L-phenylalanyl peptides of general formula Ac-Phe-(Gly)n-NH2 (n = 0-2) has been synthesized to study the effect of leaving group chain length on the efficiency of chymotrypsin A alpha amidase and peptidase activities. The effect upon catalysis of hydrophobic side chains on the leaving group was investigated using similar substrates with one of the glycine residues selectively substituted by an alanine residue as in Ac-Phe-Ala-NH2, Ac-Phe-Ala-Gly-NH2, and Ac-Phe-Gly-Ala-NH2. Values of kcat and Km have been obtained from kinetic measurements at pH 8.00 and 25 degrees C. The results are shown to be consistent with binding schemes postulated from published model building studies. The catalytic reactions were studied over a range of temperature (15-35 degrees C) and in each case the Arrhenius law was obeyed. It was thus possible to obtain meaningful values for the thermodynamic functions of activation for the acylation step of the catalytic reaction. The results are shown to confirm the findings of postulated binding schemes but indicate that conclusions drawn from kinetic measurements at a single temperature may sometimes be misleading.

Amidohydrolases↗

PubMed1987

Structure of the oligosaccharide portion of human hepatitis B surface antigen.

The hepatitis B surface antigen, which constitutes the currently available vaccine, is the empty envelope of the hepatitis B virus. We investigated the carbohydrate structures of the envelope glycoproteins. The intact oligosaccharides were enzymatically released from the coat glycoproteins using peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase F and isolated by gel permeation chromatography. Cesium ion liquid secondary ion mass spectra of the intact, underivatized oligosaccharides showed molecular weights of 1932, 2078, and 2223. The mixture included partially and totally sialylated structures, a fraction (approximately 8%) of which were substituted with a single terminal fucose residue; no desialylated oligosaccharides were detected. The reducing termini of the oligomers were derivatized by reduction of the Schiff base formed using p-aminobenzoic acid ethyl ester, and fragmentation patterns identical to those produced from standard biantennary complex oligosaccharides were obtained. Methylation linkage analysis of the oligosaccharides showed that the carbohydrate composition and the mannose branching patterns also resembled those of a biantennary oligosaccharide. The results of this study indicate that glycosylation of the hepatitis B surface antigen, which takes place in the liver, is typical of other serum glycoproteins made in the liver; and this analytical strategy, including cesium ion liquid secondary ion mass spectrometry, is an effective approach for the structural analysis of complex carbohydrates available in only the 1-10 micrograms sample size range.

Chromatography, High Pressure Liquid↗

PubMed1988

Molecular and catalytic properties of a butyrylesterase from human red cells and brain.

A butyrylesterase from human red cells was prepared to homogeneity using DEAE-cellulose, Ultrogel ACA-34, DEAE-Sephacel, and precipitation with 1.5 M (NH4)2SO4. The yield was 25-35% relative to the enzyme activity of the hemolysate. Because of its preference for butyric acid esters the enzyme was designated a butyrylesterase. With alpha-naphthyl butyrate the Km was 7.6 microM and the kcat, 48 s-1. The molecular weight was 340,000 and the subunit weight 85,000, indicating a tetrameric structure. The isoelectric pH was 4.0. The enzyme preparation did not contain cystine. Sialic acid or other carbohydrate components could not be detected. The enzyme was irreversibly inhibited by organophosphate esters and the second-order rate constant was 192 M-1 s-1 for diethyl p-nitrophenyl phosphate. For the brain enzyme the constant was 206 M-1 s-1. The enzyme was irreversibly inhibited by sulfhydryl reagents, indicating that the enzyme is a sulfhydryl-dependent serine esterase. The enzyme was identical to the butyrylesterase from human brain, and the two enzymes were immunochemically identical. An amino acid ester has been shown to be split at a higher rate than butyric acid esters; however, the specificity constant (kcat/Km) was lower for the amino acid ester than for the butyric acid ester. The enzyme did not exhibit amidase activity.

Amino Acids↗

PubMed1989

Synthesis of lipid-linked oligosaccharides in Saccharomyces cerevisiae: Man2GlcNAc2 and Man1GlcNAc2 are transferred from dolichol to protein in vivo.

Transfer of truncated oligosaccharides to protein in vivo and the structure of Man2GlcNAc2 synthesized by intact yeast (Saccharomyces cerevisiae) were investigated in the alg2 mutant. At the nonpermissive temperature the alg2 mutant accumulates lipid-linked oligosaccharides that migrate on Bio-Gel P4 in the range expected for Man2GlcNAc2 and Man1GlcNAc2 (T.C. Huffaker and P.W. Robbins (1983) Proc. Natl. Acad. Sci. USA 80, 7466-7470). We characterized the oligosaccharides, derived from protein and lipid, by comigration with standards on HPLC and by Smith degradation followed by HPLC. Man2GlcNAc2 and Man1GlcNAc2 are found on protein in alg2, since their release from a protein-containing precipitate of alg2 cells is N-glycanase (peptide-N4[N-acetyl-beta-glucosaminyl]asparagine amidase) dependent. Transfer also occurred in alg2/pAC3 cells, which carry ALG2 on a multicopy plasmid that confers partial correction of the oligosaccharide phenotype. The alg2/pAC3 cells are viable at 36 degrees C. Two isomers of Man2GlcNAc2, Man1----3ManGlcNAc2 and Man1----6ManGlcNAc2, were present on lipid and protein. The transfer of Man2GlcNAc2 and Man1GlcNAc2 to protein by intact cells supports topological models that postulate access by early intermediates to the lumen of the endoplasmic reticulum.

Borohydrides↗

PubMed1989

N-linked oligosaccharides are responsible for rat striatal dopamine D2 receptor heterogeneity.

The glycoprotein nature of the binding subunit of the dopamine D2 receptor in rat striatum has been examined by photoaffinity labeling receptor preparations with N-(p-azido-m-[125I]iodophenethyl)spiperone followed by treatment of crude membrane receptor or receptor fractions isolated from sodium dodecyl sulfate (SDS) polyacrylamide gels with endo- and exoglycosidases. The major photoaffinity labeled protein migrates as a heterogeneous species on 10% SDS polyacrylamide gels and ranges from 130,000 to 75,000 relative molecular mass (Mr). This heterogeneity can be explained by glycosylation of the receptor by complex-type N-linked oligosaccharides. Three fractions of labeled receptor were isolated from SDS polyacrylamide gels over a range of 130,000 to 75,000 Mr; after digestion with peptide-N4-[N-acetyl-beta-glucosaminyl] asparagine amidase, all fractions yielded a single peptide approximately 40,000 Mr. Treatment of photoaffinity labeled membranes with alpha-mannosidase was without effect. The dopamine D2 receptor appears to contain substantial amounts of sialic acid as treatment of photoaffinity labeled membranes with neuraminidase increased the receptor mobility on SDS polyacrylamide gels to a species of 50,000-54,000 Mr. Treatment of the receptor with neuraminidase followed by endo-alpha-N-acetylgalactosaminidase did not change the electrophoretic migration pattern from that seen after neuraminidase treatment alone, suggesting that the binding peptide contains no serine- or threonine-linked oligosaccharides. A smaller binding peptide of approximately 31,000 Mr is also apparent in crude photoaffinity labeled membranes. This material also contains N-linked oligosaccharide. Complete removal of N-linked oligosaccharide from the dopamine D2 receptor did not change the rank order potency of agonist and antagonist compounds to compete for [3H]spiperone binding to crude membrane fractions. The dopamine D2 receptor represents a highly glycosylated neural receptor.

Affinity Labels↗

PubMed1989

Asparagine catabolism in rat liver mitochondria.

A large portion of mitochondrial asparagine (Asn) is degraded by asparagine amino-transferase to produce alpha-ketosuccinamate (alpha KSA), which is then hydrolized by omega-amidase to produce oxaloacetate (OAA) and ammonia. This is in contrast to the catabolism in the cytosol, where the main catabolic route for Asn occurs initially via asparaginase-catalyzed hydrolysis to form aspartate and ammonia. Mitochondrial production of OAA from Asn was followed by monitoring the decrease in the rate of succinate oxidation (which is inhibited by OAA) in both coupled and uncoupled mitochondria. Rapid OAA production was found to be dependent on the presence of both Asn and glyoxylate, and was eliminated by the aminotransferase inhibitor, aminooxyacetate (AOX). HPLC separation and quantitation of alpha-keto acids and amino acids allowed direct observation of the proposed mitochondrial pathway. Studies using L-[U-14C]Asn in mitochondria yielded labeled carbon in alpha KSA, OAA, and CO2 when either an alpha-keto acid or glyoxylate was provided. The extent of the labeled carbon in these products was greatly influenced by factors that affected the citric acid cycle and oxidative phosphorylation. Carbon dioxide production from Asn alone, even in the presence of AOX, suggested the existence of at least one additional Asn catabolic pathway in the rat liver mitochondria which does not involve alpha KSA as an intermediate.

Animals↗

PubMed1993

Asynchronous reformation of individual kallikrein-related secretory proteinases in rat submandibular glands following degranulation by cyclocytidine.

Time scales for the reformation of the secretory granules in granular tubules and their constituent proteinases were assessed after inducing a massive degranulation by intraperitoneal injection of cyclocytidine in conscious animals. The minimum working dose of cyclocytidine to produce the maximum degranulation and depletion of proteinase activity, at 3 h after injection, was 75 mg/kg. Histologically, although most granular tubule cells then appeared to be extensively degranulated, isolated individual cells showing little or no degranulation always persisted. Acinar cells also showed some depletion of secretory material. At 15 h after injecting cyclocytidine the formation of new granules had begun in the granular tubule cells, but it was not extensive or uniform in adjacent cells; however, the acinar cells already appeared to be regranulated. The pattern of granule reformation in granular tubule cells progressed gradually, so that 7-10 days after cyclocytidine-induced degranulation the cells were mostly packed with granules and showed similar appearances to those of normal resting control glands. Individual proteinases in extracts of the glands were assayed specifically using fluorogenic oligopeptide amidase substrates, with and without appropriate inhibitors. This revealed a 95% reduction in total proteinase activity 3 h after cyclocytidine (75 mg/kg). In the same extracts, acinar peroxidase was reduced by 28%. Peroxidase levels recovered to control values within 15 h after cyclocytidine but recovery of proteinases progressed more gradually and did not occur uniformly for the different constituent proteinases. Tissue kallikrein (rK1) showed the most rapid recovery and had reached levels approaching normal within 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Ancitabine↗

PubMed1976

On the specificity of bovine spleen cathepsin B2.

The specificity of bovine spleen cathepsin B2 has been investigated by means of some natural oligo- and polypeptides, i.e. glucagon, melittin, insulin A and B chain, bradykinin, angiotensin I and II, oxytocin ACTH, clupein and salmin. The enzyme is primarily a carboxypeptidase which hydrolyzes peptide linkages of most amino acids common to proteins. In addition, cathepsin B2 displays amidase and esterase activity without requiring a free carboxyl group. The main pH optimum is between 4 and 5, in some cases higher.

Animals↗

PubMed1978

Clostridiopeptidase B inhibition by plasma marcroglobulins and microbial antiproteases.

Clostridiopeptidase B (EC 3.4.22.8) was not inhibited by stoichiometric amounts of lima bean trypsin inhibitor, ovomucoid trypsin inhibitor, Kuntiz bovine trypsin inhibotor, Kunitz soybean trypsin inhibitor or ovoinhibitor. Activity was diminished at relatively high concentrations of the three latter inhibitors. Human plasma alpha 2-macroglobulin inhibited both the amidase and protease activity of the enzyme. Rat and dog plasmas contained high molecular weight inhibitors, presumably macroglobulins as well. Inhibition by this component was greater in rat plasma than in dog plasma, which may be related to the observation that clostridiopeptidase B-induced generation of kinin activity is indirect in the former plasma, but direct in the later. Leupeptin (N-acetyl-L-leucyl-L-leucyl-L-argininal) and antipain ([S)-1-carboxy-2-phenylethyl] carbamoyl-L-arginyl-L-valyl-L-argininal) inhibited clostridiopeptidase B (Ki of 2 . 10(-8) and 3 . 10(-8) M, respectively). They were potent inhibitors of clostridiopeptidase B-induced kinin release in dog plasma.

Animals↗

PubMed1979

Studies on proteinases from Calotropis gigantea latex. II. Physico-chemichal properties of calotropain-FI and FII.

The molecular weights of purified calotropain-FI and FII were determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and by filtration of Sephadex G-100. Activation of calotropain-FI and FII by different sulfhydryl activators was studied. The results obtained from inhibition studies by various enzyme-modifying reagents suggest the possible role of cysteine and histidine residues in the active site of both the enzymes. The free and total sulfhydryl contents of both the enzymes were determined by the use of 5-5'-dithio-bis-2-nitrobenzoic acid. Total amino acid compositions of both the enzymes were also determined. A comparative study of the esterase, amidase, milk-clotting and caseinolytic activities of calotropain-FI and FII are also presented.

Amidohydrolases↗

PubMed1981

Evidence for exchange of inhibitors which bind to the active site of trypsin. Displacement of one inhibitor with a competitive inhibitor.

Two classes of inhibitors of trypsin (ED 3.4.21.4) have been studied, viz. active site-directed agents such as ovomucoid and active site titrants such as 4-methylumbelliferyl-4-guanidinobenzoate. The kinetics of beta-naphthyl-amidase inhibition by an active site-directed agent were markedly different from simultaneous assays of the availability of the active site towards active site titrants in the presence of the active site-directed agents. Analysis of these data indicated an exchange of active site-directed agent by subsequent addition of active site titrant. One class of trypsin inhibitor could be displaced by another from the trypsin active centre. Competitive chase experiments were designed to measure this exchange in which the active site-directed agent was first equilibrated with trypsin, then partially displaced by incremental additions of an active site titrant; the degree of active sites occupied by these two agents was then determined by active site titration with a second reagent.

Aprotinin↗