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PubMed1994

Structure of the Acetobacter methanolicus MB 129 capsular polysaccharide, and of oligosaccharides resulting from degradation by bacteriophage Acm7.

The capsular polysaccharide of Acetobacter methanolicus MB 129 consists of D-Glc, D-Gal, L-Rha, and L-glyceric acid in the molar ratios 1:1:1:0.3. Periodate oxidation, methylation analysis, solvolysis with HF, and detailed 1H and 13C NMR analysis resulted in the structure of the repeating unit shown below. [formula: see text] Bacteriophage Acm7-associated end-alpha-L-rhamnopyranoside hydrolase depolymerizes the CPS even in the presence of the O-acyl group, to give the respective hexa-, nona-, and dodeca-saccharides.

Acetobacter↗
PubMed1994

Factors relevant to the production of (R)-(+)-glycidol (2,3-epoxy-1-propanol) from racemic glycidol by enantioselective oxidation with Acetobacter pasteurianus ATCC 12874.

Acetobacter pasteurianus oxidizes glycidol with high activity, comparable to the oxidation of ethanol. The organism has a preference for the S-enantiomer, and the kinetic resolution process obeys a simple relationship, indicating an enantiomeric ratio (E) of 19. The compound is converted into glycidic acid, although a transient accumulation of glycidaldehyde occurs initially. Determination of other parameters revealed a temperature optimum of 50 degrees C, long-term stability (cells in the resting state), and a pH optimum compatible with the chemical stability of glycidol. However, it was also noted that respiration rates decrease at concentrations of glycidol above 1 M. This is most likely caused by substrate inhibition of the glycidol-oxidizing enzyme, the quinohemoprotein ethanol dehydrogenase. Comparison with existing methods for enantiomerically pure glycidol production indicated a number of attractive points for the method described here, although definitive evaluation must await further studies on the long-term stability under process conditions, reusability of the cells, and the mechanism of glycidol inhibition.

1-Propanol↗
PubMed1991

Cloning and sequencing of the gene cluster encoding two subunits of membrane-bound alcohol dehydrogenase from Acetobacter polyoxogenes.

The membrane-bound alcohol dehydrogenase (ADH) from Acetobacter polyoxogenes NBI1028 is composed of a 72 kDa subunit and a 44 kDa cytochrome c subunit. The amino acid sequences of the two regions of the 72 kDa subunit were determined to prepare oligonucleotides for the purpose of amplification of a DNA fragment corresponding to the intermediate region by the polymerase chain reaction. A 0.5 kb DNA fragment thus amplified was used as the probe to clone a 7.0 kb PstI fragment coding for the whole 72 kDa subunit. Nucleotide sequencing and immunoblot analysis revealed that the cloned fragment contained the full structural genes for the 72 kDa and the 44 kDa subunits and they were clustered with the same transcription polarity. The predicted amino acid sequence of the gene for the 72 kDa subunit showed homology with that of the 72 kDa subunit from ADH of A. aceti and those of methanol dehydrogenase from methylotrophic bacteria. The 72 and 44 kDa subunits contained one and three typical haem binding sequences, respectively.

Acetobacter↗
PubMed1993

Some properties of restriction endonuclease ApaBI from Acetobacter pasteurianus.

A new site-specific endonuclease has been isolated from Acetobacter pasteurianus and has been named ApaBI. The enzyme recognizes 35 cleavage sites on bacteriophage lambda DNA, 20 sites on adenovirus-2 DNA and 2 sites on plasmid pBR322. The recognition sequence for this enzyme is 3'-CGT/NNNNNACG-5' 5'-GCANNNNN/TGC-3'.

Acetobacter↗
PubMed1995

Nucleotide sequence of a small plasmid isolated from Acetobacter pasteurianus.

A 1440-bp plasmid named pAP12875 was isolated from Acetobacter pasteurianus and its nucleotide sequence determined. An open reading frame was found capable of coding for a protein that has similarity with the replication protein of pVT736-1 from Actinobacillus actinomycetemcomitans and the 32-kDa protein of phage Pf3 from Pseudomonas aeruginosa.

Acetobacter↗
PubMed2006

Alanine racemase from the acidophile Acetobacter aceti.

Acetobacter aceti converts ethanol to acetic acid, and survives acetic acid exposure by tolerating cytoplasmic acidification. Alanine racemase (Alr) is a pyridoxal 5' phosphate (PLP) -dependent enzyme that catalyzes the interconversion of the d- and l-isomers of alanine and has a basic pH optimum. Since d-alanine is essential for peptidoglycan biosynthesis, Alr must somehow function in the acidic cytoplasm of A. aceti. We report the partial purification of native A. aceti Alr (AaAlr) and evidence that it is a rather stable enzyme. The C-terminus of AaAlr has a strong resemblance to the ssrA-encoded protein degradation signal, which thwarted initial protein expression experiments. High-activity AaAlr forms lacking a protease recognition sequence were expressed in Escherichia coli and purified. Biophysical and enzymological experiments confirm that AaAlr is intrinsically acid-resistant, yet has the catalytic properties of an ordinary Alr.

Acetobacter↗
PubMed1977

Oxidation of a branched-chain alditol by acetobacter suboxydans: a stereospecific synthesis of L-dendroketose.

A synthesis of L-dendroketose (5) has been achieved by microbiological oxidation by Acetobacter suboxydans of the branched-chain alditol 2-C-(hydroxy-methyl)-D-erythro-pentitol (4). Treatment of the oxidation product with acetone, copper(II) sulfate, and sulfuric acid afforded the two di-O-isopropylidene-L-dendro-ketose derivatives 6 and 7. Assignment of configuration at the branching carbon atom (C-4) and at the anomeric center in 6 and 7 was made on the basis of the carbon-13 magnetic resonance spectra of these derivatives.

Acetobacter↗
PubMed1997

Structure of the repeating oligosaccharide from the lipopolysaccharide of the nitrogen-fixing bacterium Acetobacter diazotrophicus strain PAL 5.

Acetobacter diazotrophicus is an acid-tolerant nitrogen-fixing bacterium found in roots, rhizosphere, stems, and leaves of sugar cane (Saccharum officinarum) cultivated in Brazil. The O-polysaccharide from the lipopolysaccharide of the root isolate strain PAL 5 has been determined by a combination of methylation analysis and two-dimensional high field NMR spectroscopy. The pentasaccharide repeat has the structure: [formula: see text] Minor resonances in the NMR spectra are consistent with the presence of a proportion of repeating units which lack the beta-D-Glc side-chain.

Acetobacter↗
PubMed1997

Characterization of microbial cellulose from a high-producing mutagenized Acetobacter pasteurianus strain.

A wild-type Acetobacter pasteurianus was subjected to chemical mutagenesis for the induction and isolation of a cellulose overproducing strain. A mutagenized strain capable of synthesizing double amounts of cellulose compared to the wild type was obtained. Cellulose, both from the wild-type and the mutagenized strain, was extracted and purified for chemical characterization and investigation of its physico-chemical properties. The comparison of the two microbial polysaccharides shows that the putative mutation of A. pasteurianus strain had no effect on some cellulose features such as chemical structure, polymorphic form, crystallinity.

Acetobacter↗
PubMed1993

A novel quinoprotein methanol dehydrogenase containing an additional 32-kilodalton peptide purified from Acetobacter methanolicus: identification of the peptide as a MoxJ product.

Acetobacter methanolicus is a unique acetic acid bacterium which has a methanol oxidase respiratory chain in addition to an ethanol oxidase respiratory chain. In this study, two different forms of methanol dehydrogenase (type I and II MDHs) were purified from A. methanolicus grown on methanol. Type I MDH was more basic (pI of 8.0) and smaller (M(r) of 148K) than type II MDH (pI of 6.7 and M(r) of 177K). Type I MDH consisted of alpha and beta subunits of 62 and 10 kDa, which has the same alpha 2 beta 2 conformation as the enzymes purified so far. The type II MDH contained an additional peptide of 32 kDa, of which a single copy was estimated to bind to the alpha 2 beta 2-MDH judging from the whole molecular weight and the stoichiometry of each subunit determined in sodium dodecyl sulfate-high-performance gel filtration chromatography. Compared with type I MDH, type II MDH exhibited a lower enzyme activity, but the electron-transfer activity to cytochrome cL was much more resistant to the inhibition with NaCl or EDTA. The possibility could be excluded that type II MDH is an artificial complex of type I MDH with a 32-kDa peptide, since it was inducible with methanol and could be detected in the periplasm, as well as the other subunits. Furthermore, the N-terminal amino acid sequence of the 32-kDa peptide showed a high homology to that of the moxJ product deduced from the DNA sequence of Paracoccus denitrificans or Methylobacterium extorquens AM1.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetobacter↗
PubMed2006

Biochemical and structural studies of N5-carboxyaminoimidazole ribonucleotide mutase from the acidophilic bacterium Acetobacter aceti.

N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) mutase (PurE) catalyzes the reversible interconversion of acid-labile compounds N5-CAIR and 4-carboxy-5-aminoimidazole ribonucleotide (CAIR). We have examined PurE from the acidophilic bacterium Acetobacter aceti (AaPurE), focusing on its adaptation to acid pH and the roles of conserved residues His59 and His89. Both AaPurE and Escherichia coli PurE showed quasi-reversible acid-mediated inactivation, but wt AaPurE was much more stable at pH 3.5, with a > or = 20 degrees C higher thermal unfolding temperature at all pHs. His89 is not essential and does not function as part of a proton relay system. The kcat pH-rate profile was consistent with the assignment of pK1 to unproductive protonation of bound nucleotide and pK2 to deprotonation of His59. A 1.85 A resolution crystal structure of the inactive mutant H59N-AaPurE soaked in CAIR showed that protonation of CAIR C4 can occur in the absence of His59. The resulting species, modeled as isoCAIR [4(R)-carboxy-5-iminoimidazoline ribonucleotide], is strongly stabilized by extensive interactions with the enzyme and a water molecule. The carboxylate moiety is positioned in a small pocket proposed to facilitate nucleotide decarboxylation in the forward direction (N5-CAIR --> CAIR) [Meyer, E., Kappock, T. J., Osuji, C., and Stubbe, J. (1999) Biochemistry 38, 3012-3018]. Comparisons with model studies suggest that in the reverse (nonbiosynthetic) direction PurE favors protonation of CAIR C4. We suggest that the essential role of protonated His59 is to lower the barrier to decarboxylation by stabilizing a CO2-azaenolate intermediate.

Acetobacter↗
PubMed1997

Resonance Raman, infrared, and EPR investigation on the binuclear site structure of the heme-copper ubiquinol oxidases from Acetobacter aceti: effect of the heme peripheral formyl group substitution.

Acetobacter aceti produces two different terminal ubiquinol oxidases (cytochromes a1 and o) depending on the culture conditions. Two types of oxidases share a common protein moiety but with different heme components at the binuclear center (heme A for cytochrome a1 and heme O for cytochrome o). We investigated the structure of the binuclear site of the two oxidases using resonance Raman, Fourier transform-infrared (FT-IR), and EPR spectroscopies to clarify the interactions of heme A formyl group with protein moiety. We found that the overall architecture and the electronic configuration at the binuclear center in the oxidized state seem to be well conserved irrespective of the heme peripheral group at position 8, except for the azide-inhibited state. In contrast, we observed great variations in the C-N stretching frequency and cyanide-binding affinity in the CN-reduced state, in addition to multiple C-O stretching bands in the CO-reduced state. Present and previous studies suggest that the conformational flexibility of the binuclear center in the reduced ligand-bound state may be a common feature among the heme-copper oxidase superfamily. In the CN-reduced state, a hydrogen bond network may be formed among the formyl group, water molecule(s), and the surrounding amino acid residue(s). This network may be very important to maintain proper orientations of the distal amino acid residues and/or the CuB1+ ion relative to the cyanide ion bound to the ferrous heme iron and could play a critical role for the high affinity in cyanide binding.

Acetobacter↗
PubMed1974

Substrate specificity of an alpha-amino acid ester hydrolase produced by Acetobacter turbidans A.T.C.C. 9325.

A partially purified preparation of an alpha-amino acid ester hydrolase was obtained from Acetobacter turbidans A.T.C.C. 9325, which catalyses synthesis of 7-(d-alpha-amino-alpha-phenylacetamido)-3-cephem-3-methyl-4- carboxylic acid (cephalexin) from methyl d-alpha-aminophenylacetate and 7-amino-3-deacetoxycephalosporanic acid. The enzyme preparation catalysed both cephalosprin synthesis from 7-amino-3-deacetoxycephalosporanic acid and suitable amino acid esters (e.g. methyl d-alpha-aminophenylacetate, l-cysteine methyl ester, glycine ethyl ester, d-alanine methyl ester, methyl dl-alpha-aminoiso-butyrate, l-serine methyl ester, d-leucine methyl ester, l-methionine methyl ester) and the hydrolysis of such esters. The substrate specificity of the enzyme preparation for the hydrolysis closely paralleled the acyl-donor specificity for cephalosporin synthesis, even to the reaction rates. Only alpha-amino acid derivatives could act as acyl donors. The hydrogen atom on the alpha-carbon atom was not always required by acyl donors. The hydrolysis rate was markedly diminished by adding 7-amino-3-deacetoxycephalosporanic acid to reaction mixtures, but no effect on the total reaction rate (the hydrolysis rate plus synthesis rate) was observed with various concentrations of 7-amino-3-deacetoxycephalosporanic acid. Both the hydrolytic and the synthetic activities of the enzyme preparation were inhibited by high concentrations of some acyl donors (e.g. methyl d-alpha-aminophenylacetate, ethyl d-alpha-aminophenylacetate). The enzyme preparation hydrolysed alpha-amino acid esters much more easily than alpha-amino acid derivatives with an acid-amide bond.

Acetobacter↗
PubMed1991

The interaction of methanol dehydrogenase and cytochrome cL in the acidophilic methylotroph Acetobacter methanolicus.

The quinoprotein methanol dehydrogenase (MDH) of Acetobacter methanolicus has an alpha 2 beta 2 structure. By contrast with other MDHs, the beta-subunit (approx. 8.5 kDa) does not contain the five lysine residues previously proposed to be involved in ionic interactions with the electron acceptor cytochrome cL. That electrostatic interactions are involved was confirmed by the demonstration that methanol:cytochrome cL oxidoreductase activity was inhibited by high ionic strength (I), the strength of interaction being inversely related to the square root of I. Specific modifiers of arginine residues on MDH inhibited this reaction but not the dye-linked MDH activity. Modification of lysine residues on MDH that altered its charge had no effect on the dye-linked activity but inhibited reaction with cytochrome cL. When the charge was retained on modification of lysine residues, little effect on either activity was observed. Cross-linking experiments confirmed that lysine residues on the alpha-subunit, but not the beta-subunit, are involved in the 'docking' process between the proteins.

Acetobacter↗
PubMed1995

Isolation and enzymic properties of levansucrase secreted by Acetobacter diazotrophicus SRT4, a bacterium associated with sugar cane.

Acetobacter diazotrophicus, a nitrogen-fixing bacterium associated with sugar cane, secretes a levansucrase (sucrose-2,6-beta-D-fructan 6-beta-D-fructosyltransferase; EC 2.4.1.10). This enzyme is constitutively expressed and represents more than 70% of the total proteins secreted by strain SRT4. The purified protein consists of a single 58 kDa polypeptide with an isoelectric point of 5.5. Its activity is optimal at pH 5.0. It catalyses transfructosylation from sucrose to a variety of acceptors including water (sucrose hydrolysis), glucose (exchange reaction), fructan (polymerase reaction) and sucrose (oligofructoside synthesis). In vivo the polymerase activity leads to synthesis of a high-molecular-mass fructan of the levan type. A. diazotrophicus levansucrase catalyses transfructosylation via a Ping Pong mechanism involving the formation of a transient fructosyl-enzyme intermediate. The catalytic mechanism is very similar to that of Bacillus subtilis levansucrase. The kinetic parameters of the two enzymes are of the same order of magnitude. The main difference between the two enzyme specificities is the high yield of oligofructoside, particularly 1-kestotriose and kestotetraose, accumulated by A. diazotrophicus levansucrase during sucrose transformation. We discuss the hypothesis that these catalytic features may serve the different biological functions of each enzyme.

Acetobacter↗
PubMed1998

Decolourization and biodegradation of N,N'-dimethyl-p-phenylenediamine by Klebsiella pneumoniae RS-13 and Acetobacter liquefaciens S-1.

Klebsiella pneumoniae RS-13 and Acetobacter liquefaciens S-1, both methyl red (MR)-degrading bacterial strains, degraded N,N'-dimethyl-p-phenylenediamine (DMPD) under aerobic conditions. DMPD, a toxic and mutagenic aromatic amine, is formed during the reductive cleavage of azo dyes such as MR. The effects of physical parameters, such as temperature and aeration, and chemical parameters, such as pH and concentrations of glucose, ethanol and ammonium sulphate in the culture medium, on the degradation of DMPD by these bacteria were determined. Klebsiella pneumoniae RS-13 degraded DMPD more efficiently than A. liquefaciens S-1 under all physicochemical conditions, except in the presence of ethanol as carbon and energy sources. In addition, Kl. pneumoniae RS-13 degraded DMPD at low levels of carbon and nitrogen at pH 6-8. These results indicate that it is feasible to use Kl. pneumoniae RS-13 to completely degrade the detoxify MR under aerobic conditions.

Acetobacter↗
PubMed1998

Nucleotide sequence of the nifH gene coding for nitrogen reductase in the acetic acid bacterium Acetobacter diazotrophicus.

The nifH gene sequence of the nitrogen-fixing bacterium Acetobacter diazotrophicus was determined with the use of the polymerase chain reaction and universal degenerate oligonucleotide primers. The gene shows highest pair-wise similarity to the nifH gene of Azospirillum brasilense. The phylogenetic relationships of the nifH gene sequences were compared with those inferred from 16S rRNA gene sequences. Knowledge of the sequence of the nifH gene contributes to the growing database of nifH gene sequences, and will allow the detection of Acet. diazotrophicus from environmental samples with nifH gene-based primers.

Acetobacter↗
PubMed2002

Identification of the catalytic residues of alpha-amino acid ester hydrolase from Acetobacter turbidans by labeling and site-directed mutagenesis.

The alpha-amino acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in beta-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl aminopeptidase. The serine hydrolase inhibitor p-nitrophenyl-p'-guanidino-benzoate appeared to be an active site titrant and was used to label the alpha-amino acid ester hydrolase. Electrospray mass spectrometry and tandem mass spectrometry analysis of peptides from a CNBr digest of the labeled protein showed that Ser(205), situated in the consensus sequence, becomes covalently modified by reaction with the inhibitor. Extended sequence analysis showed alignment of this Ser(205) with the catalytic nucleophile of some alpha/beta-hydrolase fold enzymes, which posses a catalytic triad composed of a nucleophile, an acid, and a base. Based on the alignments, 10 amino acids were selected for site-directed mutagenesis (Arg(85), Asp(86), Tyr(143), Ser(156), Ser(205), Tyr(206), Asp(338), His(370), Asp(509), and His(610)). Mutation of Ser(205), Asp(338,) or His(370) to an alanine almost fully inactivated the enzyme, whereas mutation of the other residues did not seriously affect the enzyme activity. Circular dichroism measurements showed that the inactivation was not caused by drastic changes in the tertiary structure. Therefore, we conclude that the catalytic domain of the alpha-amino acid ester hydrolase has an alpha/beta-hydrolase fold structure with a catalytic triad of Ser(205), Asp(338), and His(370). This distinguishes the alpha-amino acid ester hydrolase from the Ntn-hydrolase family of beta-lactam antibiotic acylases.

Acetobacter↗