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S W Tanenbaum

Publications and source records attributed to S W Tanenbaum.

At least 19 recordsLinked to original sources
PubMed1995

Production and Characterization of Laccase from Botrytis cinerea 61-34.

An isolate of Botrytis cinerea (strain 61-34) constitutively expresses substantial amounts of extracellular laccase on a defined growth medium. The enzyme has been purified to homogeneity by a facile operational sequence, the last stage of which involves hydrophobic interaction chromatography. By these means, over 80 mg of laccase liter(sup-1) can be obtained from aerated fermentor reaction broths. The enzyme, with an estimated M(infr) of 74,000 and pI of 4.0, is a monomeric glycoprotein containing 49% carbohydrate predominantly as hexose. With 2,6-dimethoxyphenol, it exhibits a pH optimum of 3.5 and a temperature optimum of 60(deg)C, and its K(infm) is 100 (mu)M. The purified enzyme with this substrate has a specific activity of 9.1 mkat mg of protein(sup-1). Taken together with a broad substrate range and its stability in 4% sodium dodecyl sulfate or 2 M urea solutions, several biotechnology transfers are suggested.

Journal Article↗
PubMed1995

Production and rheological properties of a succinoglycan from Pseudomonas sp. 31260 grown on wood hydrolysates.

Pseudomonas sp. ATCC 31260 produced substantial amounts of anionic extracellular polysaccharide (EPS) from a mineral acid hydrolysate of wood, prepared using the "Tennessee Valley Authority" process. Partially purified EPS production approached 16.5 g/L (as hexadecyltrimethylammonium bromide precipitate) when the pH of the hydrolysate was initially adjusted to 7.5 and amended with 0.05% each of peptone and yeast extract. This EPS, now characterized as a succinoglycan, is composed of glucose, galactose, succinate, pyruvate, and acetate. Solutions of this EPS are pseudoplastic, and under specified conditions, are rheologically comparable with commercially available xanthan.

Culture Media↗
PubMed1994

Optimization of Novel Extracellular Polysaccharide Production by an Enterobacter sp, on Wood Hydrolysates.

An environmental isolate identified as Enterobacter cloacae has been found to produce a highly viscous, anionic extracellular polysaccharide (EPS) from a weak mineral acid hydrolysate of hardwood. Production of this EPS has been optimized on the hydrolysate (initial pH, 6.3; NH(4)Cl amendment, 0.1%) so that crude yields approaching 9.83 g/liter were obtained. Although this EPS is polydisperse, its molecular mass as determined by gel exclusion chromatography centers at approximately 1,700 kDa. Solutions of this EPS have been examined rheologically under a variety of conditions and compare favorably with both xanthan and alginate.

Journal Article↗
PubMed1992

Hemicellulose bioconversion to polyanionic heteropolysaccharides.

Anionic polysaccharides, traditionally obtained from plant or algal sources, have a variety of commercial uses. Such gums from microorganisms have received increased recent interest. We have initiated a program to investigate the bioconversion of pentosans to rheologically useful anionic extracellular polysaccharides (AEPS). A number of earlier-described species, including Cryptococcus laurentii, Klebsiella pneumoniae, Arthrobacter viscosus, and Pseudomonas ATCC 31260, appear to have potential in this regard. These organisms can individually convert either xylose, enzymatic oligomeric hemicellulose digests, dilute mineral acid hemicellulose ("TVA") hydrolysates, or a five-monosaccharide mixture simulating sulfite process liquors to AEPS. The formation parameters, compositions, mol-wt distributions, and the intrinsic viscosities of these purified AEPS are exemplified. Substitution of pentose as the major substrate for glucose can result in changes in mol-wt distribution or in the percentage of noncarbohydrate substituents in some AEPS. Pursuit of these observations may lead to interesting structure-property relationships and toward rheological applications for pentosan-derived AEPS.

Arthrobacter↗
PubMed1992

Heteropolysaccharide Formation by Arthrobacter viscosus Grown on Xylose and Xylose Oligosaccharides.

Arthrobacter viscosus NRRL B-1973 produces its viscous extracellular polysaccharides (EPS) when grown on media containing xylose or enzymatic xylan hydrolysates. Crude EPS formation from xylose averaged 12 g/liter when initial culture pH was adjusted to 8.0 and total nitrogen was limited to 0.03%. Purified EPS from pentose and hexose substrates were analyzed for their monosaccharide, acetyl, and uronic acid components, intrinsic viscosities, and average molecular masses. Differences were apparent in degrees of acetylation, molecular masses, and intrinsic viscosities of the heteropolysaccharides produced on different carbon sources.

Journal Article↗
PubMed1988

Photoaffinity labeling of plasma membrane receptors for cytochalasins in Ehrlich tumor cells.

Treatment of purified Ehrlich ascites cell plasma membranes either with [3H]cytochalasin B or [3H]19-O-acetylchaetoglobosin A under photolytic conditions produced several radioactive polypeptides which were characterized by SDS-PAGE analyses. The major proteins so photolabeled were in the 60,000-80,000 Da range, with less labeling found in polypeptides smaller than 43,000 and greater than 90,000 Da. Immunofluorescent staining failed to identify the major photolabeled component as actin. It is concluded, in keeping with prior investigations using other cell types, that the predominant proteins photolabeled by cytochalasins are affiliated with the glucose-transport system.

Affinity Labels↗
PubMed1984

Structure-activity relationships of cytochalasins in the differentiation of cytolytic T lymphocytes.

Four naturally occurring cytochalasins and three synthetic congeners have been studied for their effects on in vitro sensitization of murine lymphocytes to P815 mastocytoma. The relative order of effectiveness of these secondary fungal metabolites in inhibiting cytotoxic T cell development is as follows: cytochalasin D greater than cytochalasin E greater than cytochalasin A greater than cytochalasin B, 21,22- dihydrocytochalasin A greater than 7- acetylcytochalasin D. The 7,20 diacetylcytochalasin B derivative was inactive at the highest level tested (4 X 10(-6) M). Cytochalasin D is the most effective compound, producing at 5 X 10(-8) M a 50% inhibition of 51Cr release in a 4-hr cytolysis assay. This response pattern is in keeping with other test systems that implicate actin involvement, and underscores the contribution of an unsubstituted 7-hydroxyl drug function in receptor recognition. Inhibition produced by the cytochalasins is reversible if the compounds are removed from the tissue culture medium within the first 24 hr of a 4-day culture period. Delayed addition of cytochalasin D inhibits T cell development only within this first 24 hr of culture. These data suggest that the effects of cytochalasins are at an early step in the sensitization process, possibly antigen recognition.

Animals↗
PubMed1983

The interaction of substrate-related ketals with bacterial and viral neuraminidases.

Arthrobacter sialophilus neuraminidase catalyzes the hydration of 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non-2-enonic acid (2,3-dehydro-AcNeu) with Km and kcat values of 8.9 X 10(-4) M and 6.40 X 10(-4) s-1, respectively. The methyl ester of 2,3-dehydro-AcNeu as well as 2,3-dehydro-4-epi-AcNeu are also hydrated by the enzyme. The product resulting from the enzymatic hydration of 2,3-dehydro-AcNeu is N-acetylneuraminic acid. A series of derivatives of 2,3-dehydro-AcNeu (K1, 1.60 X 10(-6) M) including 2,3-dehydro-4-epi-AcNeu (2.10 X 10(-4) M) and 2,3-dehydro-4-keto-AcNeu (K1 = 6.10 X 10(-5) M) were each competitive inhibitors of the enzyme. The methyl esters of these ketal derivatives were also competitive enzyme inhibitors. Dissociation constants for these ketals were determined independently by fluorescence enzyme titrations which gave values similar to those found kinetically. These six relatives of 2,3-dehydro-AcNeu were also competitive inhibitors for the influenza viral neuraminidases. For the viral neuraminidases, the dissociation constant for 2,3-dehydro-AcNeu and its methyl ester were 2.40 X 10(-6) and 1.17 X 10(-3) M, respectively. The interpretation placed upon the K1 values determined for these ketals against the Arthrobacter versus influenza neuraminidases is that the bacterial enzyme has a more flexible glycone binding site.

Arthrobacter↗
PubMed1983

System development for linked-fermentation production of solvents from algal biomass.

Five species of the genus Dunaliella (D. tertiolecta, D. primolecta, D. parva, D. bardawil, and D. salina) were examined for glycerol accumulation, growth rate, cell density, and protein and chlorophyll content. The suitability of each algal species for use as a fermentation substrate was judged according to glycerol accumulation and quantities of neutral solvents produced after sequential bacterial fermentations. When grown in 2 M NaCl, with 24 mM NaHCO(3) or 3% CO(2) at 28 degrees C and with 10,000 to 15,000 lx of incident light on two sides of a glass aquarium, four of the five species tested produced ca. 10 to 20 mg of glycerol per liter of culture. Clostridium pasteurianum was found to convert an algal biomass mixture supplemented with 4% glycerol to ca. 16 g of mixed solvents (n-butanol, 1,3-propanediol, and ethanol) per liter. Acetone was not detected. Additionally, it has been demonstrated that Dunaliella concentrates of up to 300-fold can be directly fermented to an identical pattern of mixed solvents. Overall solvent yields were reduced by >50% when fermentations were performed in the presence of 2% NaCl. These results are discussed in terms of practical application in tropical coastal zones.

Journal Article↗
PubMed1982

The role of the conjugated carbonyl of cytochalasin A in contractility inhibitions.

A study of the mechanism of action of cytochalasin A (CA) in relation to its structural features and to its selective inhibition of certain contractile processes has been initiated. Quantitative structure-function analyses with several CA-related cytochalasins - including synthetic 21,22-dihydro-CA (DHCA), the 22-beta mercaptoethanol CA-adduct, (CA-2ME), and the 22-dithiothreitol CA-adduct (CA-DTT) - have been carried out in a temperature sensitive gel-sol extract from Ehrlich ascites tumor cells. Each drug congener was purified to homogeneity by HPLC prior to biological testing. The undiminished inhibitory indices of DHCA and CA-2ME (ID50 congruent to 3.7 x 10(-7) M) overrules the prior circumstantial evidence accumulated for the obligatory electrophilic interaction of this drug, at its alpha-beta-unsaturated ketone region, with presumptive receptor nucleophiles.

Animals↗
PubMed1982

Substrate and product specificity of Arthrobacter sialophilus neuraminidase.

Arthrobacter sialophilus neuraminidase catalyzes the hydrolysis of N-acetylneuraminyl-alpha-oxygen, nitrogen, and azido glycosides. The most effective of those substrates examined was N-acetylneuraminyl-alpha-4-methylumbelliferylglycoside (AcNeu-alpha-4-MU; Km app, 0.0193 mM; kcat, 136.4 sec-1). The products resulting from the enzymic hydrolysis of N-acetylneuraminyl-alpha-azido-glycoside were N-acetylneuraminic acid and azide ion. N-acetylneuraminyl-alpha-2,3-thiogalactylglycoside and N-acetylneuraminyl-alpha-2,6-thiogalactylglycoside were competitive inhibitors of the enzyme having KI values of 1.52 mM and 1.70 mM, respectively. Dissociation constants for these thioglycosides were also determined by fluorescence enzyme titrations which gave values similar to those determined kinetically. N-Acetylneuraminic acid, but not its methyl ester, was a competitive inhibitor of neuraminidase. Its KI value, 0.18 mM, was also determined by both methods. 5-Acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-talo-nonulosonic acid (2-deoxy-4-epi-AcNeu) was found to be a weak competitive inhibitor (KI, 12.1 mM). A. sialophilus neuraminidase further catalyzes transglycosidation reactions with methanol as acceptor. Methanol had no effect on the release of 4-MU by enzymatic hydrolysis of AcNeu-alpha-4-MU, suggesting that the formation of the enzyme-glycone intermediate is the rate-determining step. The anomeric configuration of the product of this reaction, as shown by 13C-nmr spectroscopy, is N-acetylneuraminyl-alpha-methylglycoside. Neuraminidase, therefore, catalyzes its reactions with overall retention of configuration.

Arthrobacter↗
PubMed1982

Structure-activity correlations of cytochalasins. Novel halogenated and related cytochalasin C and D derivatives.

A series of halogenated and related analogues of cytochalasin C (CC) and D (CD) has been synthesized, and the biological activities of the analogues as inhibitors in a cell-free contractility model system obtained from Ehrlich ascites tumor cells were evaluated. The reaction sequence involved treatment of CD with phenyltrimethylammonium perbromide to give 6,12-dibromo-CD (2), dehydrohalogenation of 2 to 12-bromo-CC (3), and the subsequent conversions of 3 to 12-azido- (4), 12-iodo- (5), and 12-cyano-CC (6). The ID50 values for 5, 3, 4, 2, and 6 are 6.0, 7.4, 8.8, 45, and 77 X 10(-7) M, respectively, in comparison to ca. 2.8 X 10(-7) M for the parental compounds. The potential cell and molecular biological applications of these compounds are delineated.

Animals↗
PubMed1982

Structural requirements for neuraminidase induction in Arthrobacter sialophilus.

The effectiveness of 13 N-acetylneuraminic acid derivatives as potential inducers of Arthrobacter sialophilus neuraminidase were examined. N-Acetylneuraminic acid nitrogen and thioglycosides were not inducers, whereas 2,3-dehydro-N-acetylneuraminic acid, a transition state analog for neuraminidases, was the most effective inductive ligand. The C-4 hydroxyl function of N-acetylneuraminic acid was essential for enzyme derepression.

Arthrobacter↗
PubMed1982

Structural features of cytochalasins responsible for gram-positive bacterial inhibitions.

A study of the relative effectiveness of some eighteen natural and synthetically modified cytochalasins on the uptake of glucose by the Gram-positive bacterium Arthrobacter sialophilus showed that cytochalasins B, C or D and aspochalasins A, C or D were inactive natural congeners. The presence of an alpha,beta-unsaturated carbonyl group in the macrolide moiety of these compounds with appropriate bioisosteric placement, as exemplified by cytochalasin A and aspochalasin B, are requisite molecular features. The transmembrane inhibitory index of active compounds was enhanced by increasing their lipophilicity. Thiol adducts of CA were around 20% as active in solute uptake inhibition as was the free drug. Radioactive 7-O-acetyl CA and its thiol adduct were each rapidly taken up by A. sialophilus and remained firmly bound to cellular components even after denaturant manipulations. These findings provide strong evidence for a stable association between CA and presumptive macromolecular receptors in transport and related processes.

Arthrobacter↗
PubMed1981

2,3-Dehydro-4-epi-N-acetylneuraminic acid; a neuraminidase inhibitor.

Treatment of N-acetylneuraminic acid methyl ester with sulfuric acid and acetic anhydride at 50 degrees followed by deacetylation gave 2,3-dehydro-2-deoxy-N-acetylneuraminic acid methyl ester and methyl 5-acetamido-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate (2,3-dehydro-4-epi-NeuAc methyl ester) in equal yields (approximately 40% each). The structure of the latter was ascertained primarily from analysis of its mass spectrum and 1H- and 13C-nuclear magnetic resonance spectra. The relative proportions of these two glycals in the foregoing reaction was dependent on temperature, as at 0 degrees, the yield of 2,3-dehydro-4-epi-NeuAc was markedly diminished. A minor by-product of this acetylation reaction was 2-methyl-(methyl 7,8,9-tri-O-acetyl-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate)-[ 4,5-d]-2-oxazoline. Based upon this finding and additional interconversion experiments, a mechanism involving the intermediacy of the latter oxazoline to account for the epimerization is proposed. These glycals and their methyl esters are competitive inhibitors of Arthrobacter sialophilus, neuraminidase, suggesting that the 4-hydroxyl group must be equatorially oriented for maximal enzyme inhibition.

Arthrobacter↗