43 research outputs found

    Thermal inactivation and conformational lock studies on glucose oxidase

    Get PDF
    In this study, the dissociative thermal inactivation and conformational lock theories are applied for the homodimeric enzyme glucose oxidase (GOD) in order to analyze its structure. For this purpose, the rate of activity reduction of glucose oxidase is studied at various temperatures using b-D-glucose as the substrate by incubation of enzyme at various temperatures in the wide range between 40 and 70 �C using UV–Vis spectrophotometry. It was observed that in the two ranges of temperatures, the enzyme has two different forms. In relatively low temperatures, the enzyme is in its dimeric state and has normal activity. In high temperatures, the activity almost disappears and it aggregates. The above achievements are confirmed by dynamic light scattering. The experimental parameter ‘‘n’’ as the obvious number of conformational locks at the dimer interface of glucose oxidase is obtained by kinetic data, and the value is near to two. To confirm the above results, the X-ray crystallography structure of the enzyme, GOD (pdb, 1gal), was also studied. The secondary and tertiary structures of the enzyme to track the thermal inactivation were studied by circular dichroism and fluorescence spectroscopy, respectively. We proposed a mechanism model for thermal inactivation of GOD based on the absence of the monomeric form of the enzyme by circular dichroism and fluorescence spectroscopy

    4-alpha-Glucanotransferase

    No full text

    Enzymatic Depolymerization of Starch

    No full text

    The time course of early post-mortem biochemical processes in the abdominal muscle of a commercially important decapod crustacean (Nephrops norvegicus) : implications for post-catch processing

    No full text
    The post-mortem processes in the fast abdominal muscle of the Norway lobster Nephrops norvegicus have been investigated by simulating the first 24-h post-harvest in a controlled experiment. Tissue pH and the concentrations of arginine phosphate, glycogen, L-lactate, ATP, ADP, AMP, IMP, HxR, and Hx were measured at the time of sacrifice and 3, 6, 12 and 24 h thereafter. Additionally from the nucleotide values the corresponding adenylate energy charge (AEC) was calculated. The results reveal that the post-mortem biochemical processes in the abdomen of the Norway lobster after sacrifice and during storage at 10°C are comparable to those of vertebrates. It was found that arginine phosphate was depleted from 38.5 ± 5.2 to 10.9 ± 2.9 µmol g−1 within 3 h, and anaerobic glycolysis was enhanced, so that glycogen was depleted and L-lactate accumulated. The muscle pH decreased significantly from 7.6 ± 0.1 to 7.0 ± 0.15 within 20 min and then continued to decrease at a slower rate. Most interestingly, the ATP concentration was maintained at approximately 3.5 ± 0.3 µmol g−1 for up to 12 h post-mortem. This is unusually long and indicates a special characteristic of this fast-type crustacean muscle. AMP accumulated to a maximum after 12 h and was then slowly transformed into IMP. The AEC fell from an initial value of 0.88 to only 0.17 after 24 h. When viewed in context with the fishing industry the results demonstrate that when the product is tailed (removal of the cephalothorax) upon catch, as is common practice in this industry, the result will always be an extensive post-mortem glycolytic response that will lead to an unavoidable and rapid depletion of the energy reserves resulting in a product of lesser quality
    corecore