Comparison ofPenicillium amagasakienseglucose oxidase purified as glyco- and aglyco-proteins

Glucose oxidase kinetics using MnO2 nanosheets: confirming Michaelis-Menten kinetics and quantifying decreasing enzyme performance with increasing buffer concentration

MnO₂ nanosheets and ultraviolet-visible (UV-Vis) absorbance spectroscopy are used to study glucose oxidase (GOx) kinetics. Glucose oxidation by GOx produces H₂O₂, which rapidly decomposes the nanosheets and reduces their absorption. This direct approach for monitoring glucose oxidation enables simpler, real time kinetics analysis compared to methods that employ additional enzymes. Using this approach, the present study confirms that GOx kinetics is consistent with the Michaelis-Menten (MM) model, and reveals that the MM constant increases by an order of magnitude with increasing buffer concentration. Since larger MM constants imply higher enzyme substrate concentrations are required to achieve the same rate of product formation, increasing MM constants imply decreasing enzyme performance. These results demonstrate the facility of using MnO₂ nanosheets to study GOx kinetics and, given the widespread applications of enzymes with buffers, the important sensitivity of enzyme-buffer systems on buffer concentration.

The cytometric future: it ain't necessarily flow!

Initial approaches to cytometry for classifying and characterizing cells were based on microscopy; it was necessary to collect relatively high-resolution images of cells because only a few specific reagents usable for cell identification were available. Although flow cytometry, now the dominant cytometric technology, typically utilizes lenses similar to microscope lenses for light collection, improved, more quantitative reagents allow the necessary information to be acquired in the form of whole-cell measurements of the intensities of light transmission, scattering, and/or fluorescence.Much of the cost and complexity of both automated microscopes and flow cytometers arises from the necessity for them to measure one cell at a time. Recent developments in digital camera technology now offer an alternative in which one or more low-magnification, low-resolution images are made of a wide field containing many cells, using inexpensive light-emitting diodes (LEDs) for illumination. Minimalist widefield imaging cytometers can provide a smaller, less complex, and substantially less expensive alternative to flow cytometry, critical in systems intended for in resource-poor areas. Minimalism is, likewise, a good philosophy in developing instrumentation and methodology for both clinical and large-scale research use; it simplifies quality assurance and compliance with regulatory requirements, as well as reduces capital outlays, material costs, and personnel training requirements. Also, importantly, it yields "greener" technology.

Glucose oxidase--an overview

Glucose oxidase (beta-D-glucose:oxygen 1-oxidoreductase; EC 1.1.2.3.4) catalyzes the oxidation of beta-D-glucose to gluconic acid, by utilizing molecular oxygen as an electron acceptor with simultaneous production of hydrogen peroxide. Microbial glucose oxidase is currently receiving much attention due to its wide applications in chemical, pharmaceutical, food, beverage, clinical chemistry, biotechnology and other industries. Novel applications of glucose oxidase in biosensors have increased the demand in recent years. Present review discusses the production, recovery, characterization, immobilization and applications of glucose oxidase. Production of glucose oxidase by fermentation is detailed, along with recombinant methods. Various purification techniques for higher recovery of glucose oxidase are described here. Issues of enzyme kinetics, stability studies and characterization are addressed. Immobilized preparations of glucose oxidase are also discussed. Applications of glucose oxidase in various industries and as analytical enzymes are having an increasing impact on bioprocessing.

Assay for glucose oxidase from Aspergillus niger and Penicillium amagasakiense by Fourier transform infrared spectroscopy

A simple and direct assay method for glucose oxidase (EC 1.1.3.4) from Aspergillus niger and Penicillium amagasakiense was investigated by Fourier transform infrared spectroscopy. This enzyme catalyzed the oxidation of d-glucose at carbon 1 into d-glucono-1,5-lactone and hydrogen peroxide in phosphate buffer in deuterium oxide ((2)H(2)O). The intensity of the d-glucono-1,5-lactone band maximum at 1212 cm(-1) due to CO stretching vibration was measured as a function of time to study the kinetics of d-glucose oxidation. The extinction coefficient epsilon of d-glucono-1,5-lactone was determined to be 1.28 mM(-1)cm(-1). The initial velocity is proportional to the enzyme concentration by using glucose oxidase from both A. niger and P. amagasakiense either as cell-free extracts or as purified enzyme preparations. The kinetic constants (V(max), K(m), k(cat), and k(cat)/K(m)) determined by Lineweaver-Burk plot were 433.78+/-59.87U mg(-1) protein, 10.07+/-1.75 mM, 1095.07+/-151.19s(-1), and 108.74 s(-1)mM(-1), respectively. These data are in agreement with the results obtained by a spectrophotometric method using a linked assay based on horseradish peroxidase in aqueous media: 470.36+/-42.83U mg(-1) protein, 6.47+/-0.85 mM, 1187.77+/-108.16s(-1), and 183.58 s(-1)mM(-1) for V(max), K(m), k(cat), and k(cat)/K(m), respectively. Therefore, this spectroscopic method is highly suited to assay for glucose oxidase activity and its kinetic parameters by using either cell-free extracts or purified enzyme preparations with an additional advantage of performing a real-time measurement of glucose oxidase activity.

Rapid detection of enterotoxigenic Escherichia coli O6 in water by using monoclonal antibody and a photon-counting television camera

Monoclonal antibodies (MAbs) raised against Escherichia coli O6:H16 were screened against 15 strains of E. coli and 19 non-E. coli bacteria. A MAb-luminescence assay using MAb-5.8, which shows no cross-reactions with non-E. coli bacteria, and a photon-counting television camera were developed for rapid enumeration of E. coli O6:H16 in water. The membrane filter that retained bacteria was boiled for 5 min in a buffer and incubated with biotinylated MAb-5.8. After incubation with streptavidin-peroxidase conjugate, it was reacted with luminol-based reaction mixture. Luminous image and light intensity of the filter was recorded with a Biocell Counter. Levels of E. coli O6 higher than 7 x 10(3) CFU were detected by the MAb-luminescence assay when E. coli O6 was spotted onto the membrane filter. The sample that contained E. coli O6:H16 was filtered through a membrane filter, and the filter that retained bacteria was incubated on a filter paper soaked with nutrient broth supplemented with 0.5% NaCl at 37 degrees C for 6 h. The number of light emission points on the filter correlated well with initial E. coli O6:H16 counts within the range of 1 to 3 x 10(2) CFU. The correlation coefficient was 0.89.

Comparison of relative photon flux from single cells of the bioluminescent marine bacteria Vibrio fischeri and Vibrio harveyi using photon-counting microscopy

Photon counting microscopy was used to quantify relative photon flux from 616 single sessile cells of Vibrio harveyi and 180 single sessile cells of V. fischeri. V. fischeri cells all emitted light at nearly the same level (average 15.93+/-11.48 photons/min, range 0-58.9 photons/min) when bioluminescence was induced, whereas photon flux of V. harveyi single cells was extremely variable (average 10.51+/-20.60 photons/min, range 0-211 photons/min).