Yazar "Yagar, H" seçeneğine göre listele

Listeleniyor 1 - 5 / 5
  • Küçük Resim Yok
    Öğe
    Non-covalent immobilization of quince (Cydonia oblonga) polyphenol oxidase
    (Tubitak Scientific & Technological Research Council Turkey, 2002) Yagar, H; Sagiroglu, A
    A partially purified polyphenol oxidase from quince (Cydonia oblonga) was immobilized on bentonite by simple adsorption at pH 6.8. The properties of the immobilized enzyme were compared to those of the free enzyme. Optimum pH and temperature were determined to be 9.0 and 45degreesC, respectively, showing the alteration of pH and temperature profiles by immobilization. No drastic change was observed in the K-m value after immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrates. Thermal and storage stability and reusability experiments were carried out. It was observed that the immobilized enzyme had storage stability for a period of one year but had no reusability in the batch process.
  • Küçük Resim Yok
    Öğe
    Non-covalent immobilization of quince (Cydonia oblonga) polyphenol oxidase on alumina
    (Slovensko Kemijsko Drustvo, 2002) Yagar, H; Sagiroglu, A
    Polyphenol oxidase enzyme purified partially from quince (Cydonia oblonga) was immobilized on alumina (Al2O3) by simple adsorption at pH 6.8. The properties of immobilized enzyme were compared to those of the free enzyme. Optimum pH (8.5) and temperature (45 degreesC) were determined, showing the alteration of pH and temperature profiles by immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrate and it was established that affinity was highest for catechol. K-m constant was 5 mM for catechol. Thermal and storage stability were carried out. It was observed that the immobilized enzyme had storage stability for a period of one year.
  • Küçük Resim Yok
    Öğe
    Partially purification and characterization of polyphenol oxidase of quince
    (Scientific Technical Research Council Turkey, 2002) Yagar, H; Sagiroglu, A
    Polyphenol oxidase (PPO, EC 1.14.18.1) was extracted from quince (Cydonia oblonga) by using 0.1 M phosphate buffer, pH 6.8. The polyphenol oxidase of quince was partially purified by (NH4)(2)SO4 and dialysis. Substrate specificity experiments were carried out with catechol, pyrogallol, L-DOPA, p-cresole and tyrosine. Catechol was the most suitable substrate compound for quince PPO. The Michaelis constants were 4.54 mM, 7.35mM and 17.8 mM for catechol, pyrogallol and L-DOPA, respectively at 25degreesC. The optimum pH and temperature were determined with the specific substrate catechol as 8.0 and 40degreesC, respectively. Of eight inhibitors tested L-cysteine, ascorbic acid and potassium cyanide were the most effective against quince PPO.
  • Küçük Resim Yok
    Öğe
    Some biochemical properties of polyphenol oxidase from celery
    (Taylor & Francis Inc, 2004) Yagar, H
    Polyphenol oxidase (PPO, EC 1.14.18.1) was extracted from celery roots (Apium graveolens L.) with 0.1 M phosphate buffer, pH 7.0. The PPO was partially purified by (NH4)(2)SO4 and dialysis. Substrate specificity experiments were carried out with catechol, pyrogallol, L-DOPA, p-cresol, resorcinol, and tyrosine. The Km for pyrogallol, catechol, and L-DOPA were 4.5, 8.3, and 6.2 mM, respectively, at 25degreesC. Data for V-max/K-m values, which represent catalytic efficiency, show that pyrogallol has the highest value. The optimum pH and temperature were determined with catechol, pyrogallol, and L-DOPA. Optimum pH was 7.0 for catechol and L-DOPA, and 7.5 for pyrogallol. Optimum temperatures for maximum PPO activity were 25degreesC for pyrogallol, 40degreesC for catechol, and 45degreesC for L-DOPA. Heat inactivation studies showed a decrease in enzymatic activity at temperatures above 60degreesC. The order of inhibitor effectiveness was: L-cysteine > ascorbic acid > glycine > resorcinol > NaCl.
  • Küçük Resim Yok
    Öğe
    Some properties of free and immobilized ?-amylase from Penicillium griseofulvum by solid state fermentation
    (Taylor & Francis Inc, 2006) Ertan, F; Yagar, H; Balkan, B
    alpha-Amylase was produced from Penicillium griseofulvum by an SSF technique. alpha-Amylase was immobilized on Celite by an adsorption method. Various parameters, such as effect of pH and temperature, substrate concentration, operational and storage stability, ability to hydrolyze starch and products of hydrolysis were investigated; these findings were compared with the free enzyme. The activity yield of immobilization was 87.6%. The optimum pH and temperature for both enzymes were 5.5 degrees C and 40 degrees C, respectively. The thermal, and the operational and storage stabilities of immobilized enzyme were better than that of the free enzyme. K-m and V-max were calculated from Lineweaver-Burk plots for both enzymes. K-m values were 9.1 mg mL(-1) for free enzyme, and 7.1 mg mL(-1) for immobilized enzyme. The V max of the immobilized enzyme was approximately 40% smaller than that of the free enzyme. The hydrolysis ability of the free and immobilized enzyme were determined as 99.3% and 97.9%, respectively.