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Goto K,
Mochida K,
Asahara M,
Suzuki M,
Kasai H,
Yokota A,
( 2003 ) Alicyclobacillus pomorum sp. nov., a novel thermo-acidophilic, endospore-forming bacterium that does not possess omega-alicyclic fatty acids, and emended description of the genus Alicyclobacillus. PMID : 13130044 : DOI : 10.1099/ijs.0.02546-0 Abstract >>
A thermo-acidophilic endospore-forming bacterium was isolated from a mixed fruit juice. The organism, strain 3A(T), was rod-shaped, grew aerobically at 30-60 degrees C (optimum 45-50 degrees C), pH 3.0-6.0 (optimum pH 4.0-4.5) and produced acid from various sugars. It contained menaquinone-7 as the major isoprenoid quinone. The G+C content of the DNA was 53.1 mol%. The predominant cellular fatty acids of the strain were iso-C(15 : 0), anteiso-C(15 : 0), iso-C(16 : 0), iso-C(17 : 0) and anteiso-C(17 : 0), but omega-alicyclic fatty acids, which are characteristic of the genus Alicyclobacillus, were not found in the strain. Phylogenetic analyses based on both 16S rRNA and gyrB (DNA gyrase B subunit gene) gene sequences showed that strain 3A(T) falls into the Alicyclobacillus cluster, validated by significant bootstrap values. However, strain 3A(T) did not show a close relationship to the other species of the cluster. The level of 16S rDNA similarity between strain 3A(T) and other strains of the cluster was between 92.5 and 95.5 %. The level of gyrB sequence similarity between strain 3A(T) and other strains of the cluster was between 68.5 and 74.4 %. DNA-DNA hybridization values between strain 3A(T) and phylogenetically related strains of the genera Alicyclobacillus, Bacillus and Sulfobacillus were under 13 %, indicating that strain 3A(T) represents a distinct species. On the basis of these results, strain 3A(T) should be classified as a novel Alicyclobacillus species. The name Alicyclobacillus pomorum is proposed for this organism. The type strain of Alicyclobacillus pomorum is strain 3A(T) (=DSM 14955(T)=IAM 14988(T)).
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2. |
Zhang Y,
Ju J,
Peng H,
Gao F,
Zhou C,
Zeng Y,
Xue Y,
Li Y,
Henrissat B,
Gao GF,
Ma Y,
( 2008 ) Biochemical and structural characterization of the intracellular mannanase AaManA of Alicyclobacillus acidocaldarius reveals a novel glycoside hydrolase family belonging to clan GH-A. PMID : 18755688 : DOI : 10.1074/jbc.M803409200 Abstract >>
An intracellular mannanase was identified from the thermoacidophile Alicyclobacillus acidocaldarius Tc-12-31. This enzyme is particularly interesting, because it shows no significant sequence similarity to any known glycoside hydrolase. Gene cloning, biochemical characterization, and structural studies of this novel mannanase are reported in this paper. The gene consists of 963 bp and encodes a 320-amino acid protein, AaManA. Based on its substrate specificity and product profile, AaManA is classified as an endo-beta-1,4-mannanase that is capable of transglycosylation. Kinetic analysis studies revealed that the enzyme required at least five subsites for efficient hydrolysis. The crystal structure at 1.9 angstroms resolution showed that AaManA adopted a (beta/alpha)8-barrel fold. Two catalytic residues were identified: Glu151 at the C terminus of beta-stand beta4 and Glu231 at the C terminus of beta7. Based on the structure of the enzyme and evidence of its transglycosylation activity, AaManA is placed in clan GH-A. Superpositioning of its structure with that of other clan GH-A enzymes revealed that six of the eight GH-A key residues were functionally conserved in AaManA, with the exceptions being residues Thr95 and Cys150. We propose a model of substrate binding in AaManA in which Glu282 interacts with the axial OH-C(2) in-2 subsites. Based on sequence comparisons, the enzyme was assigned to a new glycoside hydrolase family (GH113) that belongs to clan GH-A.
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3. |
Williams RJ,
Iglesias-Fernández J,
Stepper J,
Jackson A,
Thompson AJ,
Lowe EC,
White JM,
Gilbert HJ,
Rovira C,
Davies GJ,
Williams SJ,
( 2014 ) Combined inhibitor free-energy landscape and structural analysis reports on the mannosidase conformational coordinate. PMID : 24339341 : DOI : 10.1002/anie.201308334 PMC : PMC4138987 Abstract >>
Mannosidases catalyze the hydrolysis of a diverse range of polysaccharides and glycoconjugates, and the various sequence-based mannosidase families have evolved ingenious strategies to overcome the stereoelectronic challenges of mannoside chemistry. Using a combination of computational chemistry, inhibitor design and synthesis, and X-ray crystallography of inhibitor/enzyme complexes, it is demonstrated that mannoimidazole-type inhibitors are energetically poised to report faithfully on mannosidase transition-state conformation, and provide direct evidence for the conformational itinerary used by diverse mannosidases, including �]-mannanases from families GH26 and GH113. Isofagomine-type inhibitors are poor mimics of transition-state conformation, owing to the high energy barriers that must be crossed to attain mechanistically relevant conformations, however, these sugar-shaped heterocycles allow the acquisition of ternary complexes that span the active site, thus providing valuable insight into active-site residues involved in substrate recognition.
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