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  • 1
    ISSN: 1573-6903
    Keywords: Histidine decarboxylase ; histamine synthesis ; brain ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Histidine decarboxylase, the synthetic enzyme for histamine, was partially purified from regions of rat or rabbit brain rich in the enzyme. The enzyme was purified using ion exchange and hydrophobic column chromatography and chromatofocusing. Approximately 70-fold and 110-fold enrichments were attained from rat and rabbit brain, respectively. Rat and rabbit brain histidine decarboxylase had isoelectric points of pH 5.4 and 5.6, Km values of 80 μM and 120 μM histidine and Vmax values of 210 and 625 pmol histamine formed/hr-mg protein, respectively. The partially purified histidine decarboxylase from both sources was dependent on pyridoxal phosphate for maximal activity and was inhibited by α-fluoromethylhistidine, nickel chloride and cobaltous chloride but was not inhibited by impromidine, α-methyldopa, DTNB, zinc chloride or mercuric chloride. The enzyme had a broad pH optimum between pH 7.2 and 8.0. These studies provide further information on the characteristics of mammalian histidine decarboxylase from brain.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 11 (1991), S. 35-44 
    ISSN: 0887-3585
    Keywords: microcalorimetry ; thermal stability ; lysine binding ; site-directed ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The contribution of His64 to the function and stability of tissue plasminogen activator (t-PA) kringle-2 domain (His244 in t-PA numbering) has been studied by using microcalorimetric methods to compare the ligand binding and thermal denaturation behavior of wild-type kringle-2 and mutants having His64 replaced with Tyr or Phe. This site was examined because modeling studies1 suggested that the His64 side chain could play an important role in ligand binding by forming an ion-pair with the carboxylate of the ligand, L-lysine. Kringle-2 domains were expressed by secretion of the 174-263 portion of t-PA in E. coli and purified as previously described for the wild-type domain.2 Both mutant proteins retain affinity for L-lysine, although reduced three- to four-fold relative to wild-type, demonstrating that His64 does not interact with the ligand carboxylate through an ion-pair interaction or by hydrogen bonding. The H64Y substitution does result in an altered specificity of the lysine binding site with the mutant domain having greatest affinity for a ligand of 6.8 Å chain length, whereas the wild-type domain prefers an 8.8 Å long ligand. For both wild-type and mutant, the binding of the optimal chain length ligand is dominated by enthalpic effects (ΔH = -6,000 to -7,000 cal/mol) and TΔS accounts for 〈 15% of ΔG. In addition, the H64Y mutant differs from wild-type in the effect of ligand α-amino group modification on binding affinity. Based on examination of the x-ray structure recently determined for wild-type kringle-2, the specificity changes accompanying the H64Y substitution probably result from changes in side chain interactions in the lysine binding site. Thermal denaturation experiments show that the H64Y mutant is also more stable than the wild-type protein with the difference in stabilization free energy (ΔΔG) equal to 2.7 kcal/mol at 25°C and pH 3. The increased stability of the mutant appears to be related to the difference in hydrophobicity between His and Tyr.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 501-505 
    ISSN: 0887-3585
    Keywords: protein-protein interaction ; translational reinitiation ; intracistronic complementation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Frameshift mutations in a restricted portion of the arabinose operon regulatory gene araC from Escherichia coli give rise to active AraC protein, likely from the in vivo synthesis of two Incomplete fragments that are active together. Synthesis of corresponding fragments, each separately inactive, from two plasmids within cells also resulted in complementation. © 1996 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 267-274 
    ISSN: 0006-3592
    Keywords: microbial souring ; sulfate reduction ; porous media ; kinetics ; stoichiometry ; transport phenomena ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H2S) in oil field porous media. The reactor was a packed bed (50 × 5.5 cm) tubular reactor. Sea sand (140 to 375 μm) was used as the porous media. The initial indication of souring was the appearance of well-separated black spots (precipitates of iron sulfide) in the sand bed. The blackened zones expanded radially and upward through the column. New spots also appeared and expanded into the cone shapes. Lactate (substrate) was depleted and hydrogen sulfide appeared in the effluent.Analysis of the pseudo-steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in our porous media reactor system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1125-1134 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The extracellular enzymes and cell mass from the pregrown Phanerochaete chrysosporium cultures were used for the degradation of PCP. The use of both extracellular enzymes and cell mass resulted in extensive mineralization of PCP, while the action of only the crude extracellular enzymes led to the formation of a degradation intermediate (TCHD). A kinetic model, which describes the relationship among PCP degradation, initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration, was developed. Based on this model, various effects of initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration were evaluated experimentally. It was found that when initial PCP concentration is lower than 12 μmol/L, the model of a parallel-series first-order reaction is sufficient to describe the degradation process. PCP disappearance and mineralization were enhanced by increasing either the extracellular enzyme concentration or the cell mass concentration. As high as 70% of PCP mineralization could be obtained by using a higher dosage of extracellular enzymes and cell mass. Various parameters of the kinetic model were determined and the model was verified experimentally. Simulation using this model provided the criteria needed to choose rational dosages of extracellular enzymes and cell mass for the degradation of PCP. Data reported allow some insight into the function of the extracellular enzymes and cell mass of P. chrysosporium in degradation processes of toxic pollutants and assist in the design and evaluation of practical bioremediation methods.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 454-457 
    ISSN: 0006-3592
    Keywords: copper ; diffusion ; alginate gel beads ; diffusion models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The diffusivity of Cu2+, as determined by previous authors from analysis of experimental data in terms of the shrinking core (SCM) and linear absorption (LAM) models, is examined in light of the ability of the models to curve fit all the data. It is concluded from this further analysis that previous conclusions depicting the LAM to have an advantage over the SCM for predictive value are not justified. It is also shown that equally good curve fits can be obtained with a recent absorption/desorption model of diffusion which considers directly, through distribution theory, the effect of heterogeneity of material properties on the rate of diffusion. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 263-269 
    ISSN: 0006-3592
    Keywords: microbial souring ; sulfate reduction ; porous media ; kinetics ; biotransformation ; oil reservoir ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microbial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60°C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso- and n-butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H2S production rate were found at the from part of the reactor column after H2S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H2S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H2S production rate) in the present reactor after H2S production had stabilized was calculated to be 11062 ±2.22 mg sulfate-S/day g biomass. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 1127-1146 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth of Trichoderma reesei QM9414 in shake flasks at 28°C on hemicellulose substrates and bagasse resulted in rather low yields of hemicellulolytic enzymes (1.0-1.5 units/mL xylanase and 0.05-0.08 units/mL β-xylosidase). The influence of pH on the synthesis of β-xylosidase was greater than on the synthesis of xylanase. Both xylanase and β-xylosidase showed optimal activity at pH 4-5 and 55-60°C. Xylanase was stable at pH 2-10 but was heat labile and totally inactivated after 1 h at 65°C. Enzyme stability towards heat could be increased in the presence of bovine serum albumin. The β-xylosidase was more tolerant to heat, but stable over a pH range 2.5-6.0. The D-xylose inhibited both enzymes in a competitive manner. Hemicellulose (heteroxylan) was degraded to the extent of 30-40%within 24 h. The degree of hydrolysis decreased as the substrate concentration increased and increased with increased amounts of enzyme. Multiple enzyme doses resulted in increased saccharification in reduced times. The degree of hydrolysis was influenced by the amount of β-xylosidase present in the hemicellulolytic enzyme preparation. The -;xylosidase was demonstrated to play an important role in the overall conversion of heteroxylan into xylose that is analogous to the role of β-glucosidase in the saccharification of cellulose by cellulases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 1438-1442 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 273-279 
    ISSN: 0006-3592
    Keywords: coimmobilization ; Phanerochaete chrysosporium ; pentachlorophenol ; biodegradation ; adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of coimmobilizing cell mass (and/or enzyme) and adsorbent in a hydrogel matrix for biodegradation of toxic organic chemicals was introduced. Under defined experimental conditions, the coimmobilized system using activated carbon and Phanerochaete chrysosporium was compared with nonimmobilized systems for the degradation of pentachlorophenol (PCP). It was demonstrated that the coimmobilized system degraded PCP more effectively than the nonimmobilized system. A solid substrate included in the coimmobilized system could support the biodegradation. Isolation of the degrading agents from a model interrupting microorganism by the coimmobilized capsule membrane reduced the interference on the biodegradation. In simulated contaminated soil extract and sand, the coimmobilized system also exhibited higher degradative ability and stability than the nonimmobilized systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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