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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.135, #3)
Resveratrol-induced cell inhibition of growth and apoptosis in MCF7 human breast cancer cells are associated with modulation of phosphorylated akt and caspase-9 by Yan Li; Junye Liu; Xinping Liu; Kefei Xing; Yun Wang; Fuyang Li; Libo Yao (pp. 181-192).
Resveratrol (trans-3,4N,-5-trihydroxystilbene), a phytoalexin present in grapes and red wine, is emerging as a natural compound with potential anticancer properties. Here we show that resveratrol affects the growth of human breast cancer cell lines MCF7, MDA-MB-231, SK-BR-3, and Bcap-37 in a dose-dependent manner and that MCF7 is the most sensitive among the four cell lines. MCF7 cells treated with resveratrol showed typical characteristics of apoptosis including the poly (ADP-ribose) polymerase cleavage, TdT-mediated dUTP nick end labeling-positive staining, and morphologic changes. Phosphorylation of the oncogene product Akt was significantly reduced followed by decreased phosphorylation and increased processing of pro-caspase-9 on resveratrol treatment. These results indicate that resveratrol seems to exert its growth-inhibitory/apoptotic effect on the breast cancer cell line MCF7 via the Akt-caspase-9 pathway.
Keywords: Apoptosis; resveratrol; MCF7; Akt; caspase-9
Purification, characterization, kinetic properties, and thermal behavior of extracellular polygalacturonase produced by filamentous fungus Tetracoccosporium sp by Saeed Aminzadeh; Hossein Naderi-Manesh; Khosro Khajeh; Mehdi Naderi-Manesh (pp. 193-208).
For the first time, a polygalacturonase from the culture broth of Tetracoccosporium sp. was isolated and incubated at 30°C in an orbital shaker at 160 rpm for 48h. The enzyme was purified by ammonium sulfate precipitation and two-step ion-exchange chromatography and had an apparent molecular mass of 36 kDa, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Its optimum activity was at pH 4.3 and 40°C, and the K m and V max values of this enzyme (for polygalacturonic acid) were 3.23 mg/mL and 0.15 μmol/min, respectively. Ag+, Co2+, EDTA, Tween-20, Tween-80, and Triton X-100 stimulated polygalacturonase activity whereas Al3+, Ba2+, Ca2+, Fe2+, Fe3+, Ni2+, Mg2+, Mn2+, and SDS inhibited it. In addition, iodoacetamide and iodoacetic acid did not inhibit enzyme activity at a concentration of 1 mM, indicating that cysteine residues are not part of the catalytic site of polygalacturonase. We studied the kinetic properties and thermal inactivation of polygalacturonase. This enzyme exhibited a t 1/2 of 63 min at 60°C and its specific activity, turnover number, and catalytic efficiency were 6.17 U/mg, 113.64 min−1, and 35.18 mL/(min·mg), respectively. The activation energy (ΔE #) for heat inactivation was 5.341 kJ/mol, and the thermodynamic activation parameters ΔG #, ΔH #, and ΔS # were also calculated, revealing a potential application for the industry.
Keywords: Polygalacturonase; Tetracoccosporium sp.; kinetic properties; thermal stability; thermodynamic activation parameters; purification
Optimization of a high-performance liquid chromatography method to quantify bilirubin and separate it from its photoproducts by A. M. H. Al-Hamdi; J. R. Williams; S. M. Z. Al-Kindy; A. E. Pillay (pp. 209-218).
A rapid reversed-phase (RP) high-performance liquid chromatography method for the isolation of bilirubin from its photoproducts (e.g., biliverdin) is reported. The method is based on isocratic elution using methanol:water as the mobile phase. A 24 full-factorial experimental design approach was adopted. For the optimization, the best separation was obtained using a flow rate of 1.50 mL/min, a mobile phase of 99∶1 methanol:water (v/v) at pH 3.60, and a 150×4.6 mm id RP (C18) column containing 5-μm particles. These conditions produced the fastest total retention time of 3.38±0.055 min, and other chromatographic parameters were acceptable. Under the optimum conditions, a linear calibration curve for bilirubin was obtained over the 1.0–40.0 μg/L concentration range studied. The limit of quantification was 0.79 g/L and the limit of detection was 0.24 μg/L. Bilirubin in solution was monitored by ultraviolet detection at 450 nm.
Keywords: Bilirubin; biliverdin; experimental design; reversed-phase chromatography; isocratic elution
Complete bioconversion of hemicellulosic sugars from agricultural residues into lactic acid by Lactobacillus pentosus by A. B. Moldes; A. Torrado; A. Converti; J. M. Domínguez (pp. 219-227).
On the basis of previous knowledge, different agroindustrial wastes were submitted to dilute-acid hydrolysis with H2SO4 to obtain hemicellulosic sugars and then employed for lactic acid production by Lactobacillus pentosus. Toxic compounds released from lignin did not affect lactic acid fermentation when hydrolysates from trimming vine shoots, barley bran husks, or comcobs were employed as carbon source, and complete bioconversion of hemicellulosic sugars was achieved. Nevertheless, Eucalyptus globulus hydrolysates had to be submitted to a detoxification process with activated charcoal. Maximum lactic acid concentration (33 g/L) was reached employing barley bran hydrolysates, whereas corncobs, trimming vine shoots, and detoxified E. globulus hydrolysates yielded 26, 24, and 14.5 g/L of lactic acid, respectively. The maximum product yield from pentoses (0.76 g/g) was achieved using hydrolysates from trimming vine shoots, followed by hydrolysates from detoxified E. globulus (0.70 g/g), barley bran (0.57 g/g), and corncob (0.53 g/g). These results confirm that L. pentosus can be employed to ferment hemicellulosic sugars (mainly xylose, glucose, and arabinose) from acid hydrolysates of most agricultural residues without appreciable substrate inhibition.
Novel core-shell nanoparticles and their application in high-capacity immobilization of enzymes by Xuepu Mao; Jinfeng Huang; Man Fai Leung; Zhiyun Du; Lin Ma; Zhishu Huang; Pei Li; Lianquan Gu (pp. 229-239).
Novel core-shell nanoparticles consisting of poly(methyl methacrylate) (PMMA) cores coated with synthetic polymer and biopolymer (polyethyleneimine, chitosan, and casein) shells were synthesized via direct graft copolymerization of methyl methacry late from hydrophilic polymers in the absence of surfactant. Average hydrodynamic diameters of the nanoparticles ranged from 163 to 263 nm. High-capacity (up to 530 mg/g) immobilizations of enzymes and high-activity retained percentage (E spe) (up to 90%) were achieved.
Keywords: Core shell; poly(methyl methacrylate); nanoparticles; immobilized cellulase