Browsing by Author "Tozlu, I"

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Polyphenol Oxidase From Allium Sp
(Amer Chemical Soc, 1997) Arslan, O; Temur, A; Tozlu, I
Polyphenol oxidase (PPO) was isolated from Allium sp. PPO showed activity to catechol and DL-dopa (K-m values were 25 mM for cathecol and 33 mM for DL-dopa; V-max values were 666 EU/mL . min for cathecol and 166 EU/mL . min for DL-dopa). Catechol was the most suitable substrate for Allium sp. PPO (lowest K-m value). The optimum pH for the PPO was 7.5 on substrates catechol and DL-dopa. Heat inactivation studies showed temperature >40 degrees C resulted in loss of enzyme activity. Heating for 30 min at 40 degrees C did not cause a significant loss of enzymatic activity. Allium sp. PPO was significantly inhibited in the presence of ascorbic acid, 2-mercaptoethanol, and sodium metabisulfide.
Polyphenol Oxidase From Malatya Apricot (Prunus Armeniaca L.)
(Amer Chemical Soc, 1998) Arslan, O; Temur, A; Tozlu, I
Polyphenol oxidase (PPO) of Malatya apricot was isolated by (NH4)(2)SO4 precipitation and dialysis. PPO showed activity to catechol, L-dopa, and gallic acid. Catechol was the most suitable substrate for Malatya apricot PPO (lowest K-m value). The optimum pH for the PPO was 8.5. Heating for 40 min at 40 degrees C did not cause a significant loss of enzymic activity. The times required for 50% inactivation of activitiy at 60 and 80 degrees C were found to be 47 and 16 min, respectively. The I-50 values of inhibitors studied on PPO were determined by means of activity percentage [I] diagrams. The values were 2.7 x 10(-5), 5.03 x 10(-5), 3.62 x 10(-5), 3.68 x 10(-5), and 8.30 x 10(-4) M for sodium metabisulfite, ascorbic acid, 2-mercaptoethanol, thiourea, and salicylic acid, respectively. Ascorbic acid, 2-mercaptoethanol, sodium metabisulfite, and thiourea inhibited the reaction strongly.
Studies on the Reactions of 4-Ethoxycarbonyl With Some Nh Nucleophiles
(Tubitak Scientific & Technological Research Council Turkey, 2004) Sener, A; Genç, H; Tozlu, I; Sener, MK
4-Ethoxycarbonyl-5-phenyl-2,3-dihydro-2,3-furandione 1 was reacted with o-phenylenediamine, substituted ureas and methylcarbamate or acetamide to give quinoxaline 2, pyrimidine 3 and benzoylmalonic acid 4 derivatives, respectively. Benzoylmalonic acid derivative 4a was converted into a new oxozinedione derivative, 5, by refluxing its solution in xylene containing a catalytic amount of p-toluene sulfonic acid. In addition, triphenylpyrazole carboxylic acid derivative 6 was obtained from the reaction of 4a with diphenylhydrazine.
Substrate Specificity, Heat Inactivation and Inhibition of Polyphenoloxidase From Anethum Graveolens L
(Chiriotti Editori, 1997) Arslan, O; Tozlu, I
Polyphenoloxidase (PPO), isolated from Anethum graveolens L, showed activity on catechol, L-tyrosine and DL-DOPA. The optimum pH for the PPO was 7.0. Heat inactivation studies showed that heating for 40 and 15 min at 60 degrees and 80 degrees C, respectively, caused a 50% loss in enzymatic activity. The enzyme catalysed browning reaction was significantly inhibited in the presence of ascorbic acid, 2-mercaptoethanol, uric acid and barbituric acid. The most effective inhibitors were ascorbic acid and 2-mercaptoethanol.