Polyphenol oxidase (PPO) was extracted from Emir grapes grown in Turkey and its characteristics in terms of pH and temperature optima, thermal inactivation, kinetic parameters and potency of some PPO inhibitors were studied. The optimum pH and temperature for grape PPO were found to be 4.2 and 25 • C respectively using catechol as substrate. K m and V max values were found to be 25.1 ± 2.72 mmol L −1 and 0.925 ± 0.04 OD 410 min −1 respectively. Of the inhibitors tested, the most potent was sodium metabisulfite, followed by ascorbic acid. The thermal inactivation curve was biphasic. Activation energy (E a ) and Z values were calculated as 251.4 kJ mol −1 (r 2 = 0.996) and 8.92 • C (r 2 = 0.993) respectively.

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ABSTRACT. This paper summarizes the recent evidence for combined therapies in the intravitreal medical treatment of diabetic macular oedema or macular oedema, secondary to retinal vein occlusion. Since the introduction of anti-inflammatory or anti-VEGF drugs combined with or used alternatively to laser, visual acuity can be stabilized or improved in a significant number of patients. However, there is an ongoing debate regarding the safety, efficiency and economic concerns related to these intravitreal monotherapies because they warrant frequent repetition to maintain the clinical effect. In the literature, the combination of photolasercoagulation, intravitreal steroids or VEGF-inhibitors, or both, shows early compelling evidence that some patients may benefit from less retreatment compared to monotherapy. To provide a conceptual and perspective approach for a first-line combined therapy, this paper also summarizes own results of pilot interventional case series of a 1.5 cc core pars plana vitrectomy and intravitreal substitution with balanced salt solution (BSS), 1.25 mg bevacizumab and 8 mg triamcinolone.

The extent of ADP-ribosylation in rectal cancer was compared to that of the corresponding normal rectal tissue. Twenty rectal tissue fragments were collected during surgery from patients diagnosed as having rectal cancer on the basis of pathology results. The levels of ADP-ribosylation in rectum cancer tissue samples (95.9 ± 22.1 nmol/ ml) was significantly higher than in normal tissues (11.4 ± 4 nmol/ml). The level of NAD + glycohydrolase and ADP-ribosyl cyclase activities in rectal cancer and normal tissue samples were measured. Cancer tissues had significantly higher NAD + glycohydrolase and ADPribosyl cyclase activities than the control tissues (43.3 ± 9.1 vs 29.2 ± 5.2 and 6.2 ± 1.6 vs 1.6 ± 0.4 nmol mg -1 min -1 ). Approximately 75% of the NAD + concentration was consumed as substrate in rectal cancer, with changes in NAD + /ADP-ribose metabolism being observed. When [ 14 C]-ADP-ribosylated tissue samples were subjected to SDS-PAGE, autoradiographic analysis revealed that several proteins were ADPribosylated in rectum tissue. Notably, the radiolabeling of a 113-kDa protein was remarkably greater than that in control tissues. Poly(ADP)-ribosylation of the 113-kDa protein in rectum cancer tissues might be enhanced with its proliferative activity, and poly(ADP)-ribosylation of the same protein in rectum cancer patients might be an indicator of tumor diagnosis.

This study was undertaken to investigate the correlation between browning degree and composition of important Turkish white wine grape varieties during the 2006 and 2007 seasons. Large seasonal and cultivar variations were found in all measured variables. The highest browning degree was found in the Narince cultivar in both years, followed by Emir and Sultaniye, with Narince being the most susceptible to browning and Sultaniye being the least. No correlation (P < 0.05) was found between browning degrees and cysteine, glutathione, polyphenol oxidase activity, or total phenolic contents. Effects of harvest year and variety on all measured parameters, except total phenolics, were statistically significant (P < 0.01).

Polyphenol oxidase (PPO) was extracted and purified from Goldnugget loquat and its characteristics were studied. Two protein peaks containing PPO activity were recovered, which were denoted as isoenzyme A and isoenzyme B. A 5.7-fold purification of isoenzyme A with a recovery of 15.3% and 61.1-fold purification of isoenzyme B with a recovery of 98.9% were achieved. Assay of activity of the isoenzymes between pH 3.04 and 7.80 using catechol as substrate showed two activity peaks, one at acidic pH and the other at neutral pH. pH optima of isoenzyme A and B were found to be at 4.5 and 6.8, respectively. Isoenzyme A exhibited a higher activity at acidic pHs than isoenzyme B. They both displayed maximal activity at 30C. Thermal resistance of isoenzyme A was found to be higher than that of isoenzyme B. Effect of inhibitors on the isoenzymes varied markedly. PRACTICAL APPLICATIONEnzymatic browning catalyzed by polyphenol oxidase (PPO) is generally considered to be detrimental to food quality from both organoleptic and nutritional points of view. Polyphenol oxidase-catalyzed browning reactions in fruits and vegetables during handling and processing impairs the sensory properties and marketability of the product and also lowers the nutritional value. An understanding of the essential factors controlling the action of PPO is necessary in an attempt to inhibit or control PPO activity in fruit and vegetables during processing. Therefore, it is important to control the PPO activity, as well as to determine its characteristics associated with the variety.

This research was carried out to determine biochemical properties of β-glucosidase (β-D-glucoside glucohydrolase, EC 3.2.1.21) isolated from Turkish tea leaves. Two protein peaks containing β-glucosidase activity were recovered and characterized, which were denoted as isoenzyme A and isoenzyme B. Their pH optimum, thermal resistances, affinity towards p-nitrophenyl-β-D-glucopyranoside differed markedly. They both displayed maximal activity at pH 5.0. The effects of the inhibitors tested varied in a dose dependent manner.

Akko XIII is an important loquat variety grown in Turkey. As with many fruits and vegetables, enzymatic browning catalyzed by polyphenol oxidase (PPO) also occurs in loquats. PPO from Akko XIII loquat was extracted and purified through (NH 4 ) 2 SO 4 precipitation, dialysis and ion exchange chromatography. The enzyme showed several peaks with PPO activity on DEAE-Toyopearl 650 M column, of which only two (isoenzyme A and isoenzyme B) were characterized. Assay of activity of the isoenzymes between pH 3.04 and 7.80 using catechol as substrate showed two activity peaks, one at acidic pH and the other at neutral pH. pH optima of isoenzyme A and B were found to be at 7.4 and 4.98, respectively. The Km values of isoenzyme A and B using catechol as substrate were found to be 152.3 mM and 5.4 mM, respectively. They both displayed maximal activity at 30 o C. The two isoenzymes displayed different heat resistance and sensitivity towards various inhibitors.