T. Güray - Academia.edu (original) (raw)

Papers by T. Güray

Journal of Food Protection, 1998

In this study, biochemical properties of two extracellular β-lactamases produced by penicillin-re... more In this study, biochemical properties of two extracellular β-lactamases produced by penicillin-resistant Streptococcus thermophilus cells were investigated. Both β-lactamases showed specificity for penicillins but not for cephaloridins. The β-lactamases exhibited different affinities for penicillin G. The one with the higher molecular weight (FI) had a Km value of 3.44 μM and a Vmax value of 8.33 μmol/min/mg of protein, whereas the β-lactamase with the lower molecular weight (FII) had a Km value of 4.76 μM and a Vmax value of 3.13 μmol/min/mg of protein. Both β-lactamases were inhibited by iodine, copper sulfate, and iron sulfate but not by EDTA. The optimal pH ranged between 6 and 7, and the optimal temperatures were between 40 and 45°C for both enzymes.

Neoplasma, 2006

In this study, arylamine N-acetyltransferases, NATs (E.C.2.3.1.5) and glutathione-S-transferase-T... more In this study, arylamine N-acetyltransferases, NATs (E.C.2.3.1.5) and glutathione-S-transferase-T2-2, GSTT2-2 (E.C.2.5.1.18) enzyme activities in the breast tumor and surrounding tumor-free tissues of 22 female breast cancer patients with infiltrating ductal carcinoma were measured. The possible impacts of grade of malignancy, chemotherapy treatment, estrogen receptor status and menopausal status on all enzyme activities were evaluated. The results showed that, both NAT2 and GSTT2-2 display significant differences between tumor and tumor-free breast tissues, while no difference was observed in NAT1. Grade of malignancy seems to be positively associated with NAT1 and negatively associated with GSTT2-2. Though, both NAT2 and GSTT2-2 have increased mean tumor activities, the grade of malignancy, chemotherapy status, menopausal status or estrogen receptor status are not correlated statistically.

Neoplasma, 2001

N-Acetyltransferase activities were determined in tumor (12 malignant and 6 benign) and control (... more N-Acetyltransferase activities were determined in tumor (12 malignant and 6 benign) and control (non-cancerous) breast tissues from 18 female patients. The activities of matched 12 malignant tumor and control tissue cytosols showed 6 rapid, 4 intermediate and 2 slow acetylators based on p-aminobenzoic acid (NAT1) and sulfamethazine (NAT2) as substrates. Compared to the activities of slow acetylators, the rapid acetylators exhibited mean apparent Vmax values about 5- and 50-fold greater for p-aminobenzoic acid and sulfamethazine, respectively. No correlation was observed between the blood and breast tissue N-acetyltransferase (NAT1 and NAT2) activities. When the mean apparent N-acetyltransferase activities of the malignant and benign breast tumor tissues were compared, the results showed an increased activity for both p-aminobenzoic acid (PABA) and sulfamethazine (SMZ) acetylation in the malignant tissues compared to benign ones, and also control tissues showed lower activities compa...

Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1992

Two forms of soluble NADH cytochrome b 5 reductase were purified from human erythrocytes. Two dis... more Two forms of soluble NADH cytochrome b 5 reductase were purified from human erythrocytes. Two distinct fractions both having the NADH cytochrome b5 reductase activity eluted from the second DEAE-cellulose column were further purified by ultrafiltration and 5'-ADP-agarose affinity chromatography. 2. The final preparations were purified 9070-and 4808-fold, respectively, over hemolysate. Both reductases exhibited identical electrophoretic patterns when subjected to SDS-PAGE and apparent monomer M, of each reductase was determined to be 32,000 _+ 1300. 3. Vm~ values ofreduetase II for the various electron aeeeptors, namely, 2,6-dichlorophenolindophenol, ferricyanide and cytochrome c through cytochrome bs were found to be 1.9, 1.8 and 2 times higher than those of reductase I. 4. Some differences were noted for reductase I and reductase II fractions. Their elution profiles from a second DEAE-cellulos¢ column were quite different and that suggested that reductase II is more acidic than reductase I. Reductase II was found to be more sensitive to heat treatment than reductase I.

International Journal of Biochemistry, 1991

1. Lung NADH-cytochrome b5 reductase was saturated with its artificial substrate, potassium ferri... more 1. Lung NADH-cytochrome b5 reductase was saturated with its artificial substrate, potassium ferricyanide at approximately 0.1 mM ferricyanide concentration, and the activity of the lung enzyme was inhibited by the higher concentrations of potassium ferricyanide. Ferricyanide at 0.5 and 1.0 mM inhibited the activity of the enzyme by about 20 and 61% respectively. The apparent Km value was calculated as 13.7 microM potassium ferricyanide and 4.3 microM NADH. 2. The Michaelis constants for cytochrome b5 and NADH were determined to be 1.67 and 7.7 microM from the Lineweaver-Burk plots. These results demonstrate that affinity of the lung reductase for its natural substrate is almost 10 times higher than that for potassium ferricyanide. 3. Addition of non-ionic detergent stimulated the rate of reductase-catalyzed reduction of lung cytochrome b5 up to 8.2-fold. 4. Kinetic studies performed with lung reductase by varying NADH and cytochrome b5 concentrations at different fixed concentrations at cytochrome b5 or NADH showed a series of parallel lines indicating a "ping-pong" type of kinetic mechanism for interaction of NADH and cytochrome b5 with lung cytochrome b5 reductase.

European Journal of Clinical Pharmacology, 1994

One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5... more One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5 mg coumarin p.o. after an overnight fast. Urine samples were collected before and 2, 4 and 8 h after drug administration. The extent and rate of formation of 7-OHcoumarin (7OHC) was determined by the urinary excretion of the metabolite as measured with the fluorometric method. On average, 80 % of 7OHC formed was excreted in 2 h. The total amount of 7OHC formed was 59.8 % (21.5 %) (mean and SD, n = 100, range 17-100 %) of the given dose. The percentage of 7OHC excreted during the first 2 h compared with the 7OHC excretion at 8 h was a constant and stable individual characteristic for the rate of the formation of 7OHC ('2 h coumarin test'). Although four individuals had relatively slow coumarin test values (34-40 %), no clear-cut polymorphism in the rate of 7OHC formation was found. However, 7OHC formation was lower in males and in cigarette smokers. Key words Coumarin, Coumarin 7-hydroxylation; interindividual variability, polymorphism Coumarin, a naturally occurring plant product, has been used clinically in postthrombotic syndromes, varicose insufficiency, and posttraumatic oedema [1]. Recently, the use of coumarin in the treatment of cancer and chronic brucellosis has also been reported [1, 2]. The scientific contents of this paper contribute to the goals of the COST B1 project.

Diabetes/Metabolism Research and Reviews, 2012

Background In diabetes mellitus, increased formation of reactive oxygen species due to high level... more Background In diabetes mellitus, increased formation of reactive oxygen species due to high level of glucose in both blood plasma and tissues creates oxidative stress and damages the tissues. Antioxidants together with the antioxidant enzymes are very important in order to protect the cells against oxidative damage. Methods Differential expressions of both mRNA and proteins of major antioxidant enzymes in streptozotocin-induced diabetic rat kidneys were measured with the help of real-time polymerase chain reaction and western blot analysis, respectively. Furthermore, effects of two strong antioxidants a-lipoic acid, vitamin C and their combination on the regulation of both expressions and the activities of antioxidant enzymes were also studied. Results In diabetic rat kidney tissue, both catalase and glutathione peroxidase activities were reduced (although mRNA expression for both was greatly increased) when compared with controls. No significant change was observed in superoxide dismutase (SOD) activity. Alpha-lipoic acid increased catalase activity towards the control values. Combined administration of alpha-lipoic acid and vitamin C increased the activities of both catalase and SOD, demonstrating a posttranslational effect. Glutathione concentrations were decreased in diabetic kidney; alpha-lipoic acid treatment partially restored the glutathione levels.

Studies in Organic Chemistry, 1998

A chitosan degrading fungus was isolated from chitosan and then identified as Penicillium spinulo... more A chitosan degrading fungus was isolated from chitosan and then identified as Penicillium spinulosum by the International Mycological Institute, England. The isolate was used for the production of chitosanase in a salts medium with either chitosan or Rhizopus cell walls as the sole carbon source. Chitosanase was produced under all the conditions tested, however better yields were obtained by using Rhizopus cell walls.

Toxicology in Vitro, 1995

The reduction of nitrofurantoin by purified liver nitrofurantoin reductase was followed by the pr... more The reduction of nitrofurantoin by purified liver nitrofurantoin reductase was followed by the production of superoxide radicals, which were detected by the reduction of epinephrine. The conditions for the formation of superoxide radicals were optimized. The maximum superoxide radical formation occurred at approximately 3.5 μg purified reductase, with optimum pH of 7.8 and at 0.05 mm nitrofuran- toin concentration. The

Archives of Toxicology, 1991

Treatment of rabbits with benzene (880 mg/kg/day), s.c. for 3 consecutive days, caused 3.8- and 5... more Treatment of rabbits with benzene (880 mg/kg/day), s.c. for 3 consecutive days, caused 3.8- and 5.7-fold increases in aniline 4-hydroxylation rates of liver and kidney microsomes, respectively. Benzene treatment markedly enhanced hydroxylation rats of p-nitrophenol by liver and kidney by 7.2- and 4.2-fold, respectively. Both of these enzymes are associated with cytochrome P-450 LM3a. In contrast, the activity of benzphetamine N-demethylase, associated with P-450 LM2, was not altered significantly in either liver or kidney microsomes. Although the total cytochrome P-450 contents of liver and kidney microsomes were not altered significantly by the benzene treatment, in the case of liver microsomes, formation of a new cytochrome P-450 with an apparent Mr of 51,400 was observed on SDS-PAGE. On the other hand, in the kidney microsomes, the intensity of the bands corresponding to approximate Mr of 50,000 and 51,400 was markedly increased. The results of the present work, in combination with those of the previous work (Arinç et al. 1988), indicate the existence of tissue specificity in the induction of rabbit P-450 isozyme by benzene.

European Journal of Clinical Pharmacology, 1994

One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5... more One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5 mg coumarin p.o. after an overnight fast. Urine samples were collected before and 2, 4 and 8 h after drug administration. The extent and rate of formation of 7-OHcoumarin (7OHC) was determined by the urinary excretion of the metabolite as measured with the fluorometric method.

Journal of Food Protection, 1998

In this study, biochemical properties of two extracellular β-lactamases produced by penicillin-re... more In this study, biochemical properties of two extracellular β-lactamases produced by penicillin-resistant Streptococcus thermophilus cells were investigated. Both β-lactamases showed specificity for penicillins but not for cephaloridins. The β-lactamases exhibited different affinities for penicillin G. The one with the higher molecular weight (FI) had a Km value of 3.44 μM and a Vmax value of 8.33 μmol/min/mg of protein, whereas the β-lactamase with the lower molecular weight (FII) had a Km value of 4.76 μM and a Vmax value of 3.13 μmol/min/mg of protein. Both β-lactamases were inhibited by iodine, copper sulfate, and iron sulfate but not by EDTA. The optimal pH ranged between 6 and 7, and the optimal temperatures were between 40 and 45°C for both enzymes.

Neoplasma, 2006

In this study, arylamine N-acetyltransferases, NATs (E.C.2.3.1.5) and glutathione-S-transferase-T... more In this study, arylamine N-acetyltransferases, NATs (E.C.2.3.1.5) and glutathione-S-transferase-T2-2, GSTT2-2 (E.C.2.5.1.18) enzyme activities in the breast tumor and surrounding tumor-free tissues of 22 female breast cancer patients with infiltrating ductal carcinoma were measured. The possible impacts of grade of malignancy, chemotherapy treatment, estrogen receptor status and menopausal status on all enzyme activities were evaluated. The results showed that, both NAT2 and GSTT2-2 display significant differences between tumor and tumor-free breast tissues, while no difference was observed in NAT1. Grade of malignancy seems to be positively associated with NAT1 and negatively associated with GSTT2-2. Though, both NAT2 and GSTT2-2 have increased mean tumor activities, the grade of malignancy, chemotherapy status, menopausal status or estrogen receptor status are not correlated statistically.

Neoplasma, 2001

N-Acetyltransferase activities were determined in tumor (12 malignant and 6 benign) and control (... more N-Acetyltransferase activities were determined in tumor (12 malignant and 6 benign) and control (non-cancerous) breast tissues from 18 female patients. The activities of matched 12 malignant tumor and control tissue cytosols showed 6 rapid, 4 intermediate and 2 slow acetylators based on p-aminobenzoic acid (NAT1) and sulfamethazine (NAT2) as substrates. Compared to the activities of slow acetylators, the rapid acetylators exhibited mean apparent Vmax values about 5- and 50-fold greater for p-aminobenzoic acid and sulfamethazine, respectively. No correlation was observed between the blood and breast tissue N-acetyltransferase (NAT1 and NAT2) activities. When the mean apparent N-acetyltransferase activities of the malignant and benign breast tumor tissues were compared, the results showed an increased activity for both p-aminobenzoic acid (PABA) and sulfamethazine (SMZ) acetylation in the malignant tissues compared to benign ones, and also control tissues showed lower activities compa...

Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1992

Two forms of soluble NADH cytochrome b 5 reductase were purified from human erythrocytes. Two dis... more Two forms of soluble NADH cytochrome b 5 reductase were purified from human erythrocytes. Two distinct fractions both having the NADH cytochrome b5 reductase activity eluted from the second DEAE-cellulose column were further purified by ultrafiltration and 5'-ADP-agarose affinity chromatography. 2. The final preparations were purified 9070-and 4808-fold, respectively, over hemolysate. Both reductases exhibited identical electrophoretic patterns when subjected to SDS-PAGE and apparent monomer M, of each reductase was determined to be 32,000 _+ 1300. 3. Vm~ values ofreduetase II for the various electron aeeeptors, namely, 2,6-dichlorophenolindophenol, ferricyanide and cytochrome c through cytochrome bs were found to be 1.9, 1.8 and 2 times higher than those of reductase I. 4. Some differences were noted for reductase I and reductase II fractions. Their elution profiles from a second DEAE-cellulos¢ column were quite different and that suggested that reductase II is more acidic than reductase I. Reductase II was found to be more sensitive to heat treatment than reductase I.

International Journal of Biochemistry, 1991

1. Lung NADH-cytochrome b5 reductase was saturated with its artificial substrate, potassium ferri... more 1. Lung NADH-cytochrome b5 reductase was saturated with its artificial substrate, potassium ferricyanide at approximately 0.1 mM ferricyanide concentration, and the activity of the lung enzyme was inhibited by the higher concentrations of potassium ferricyanide. Ferricyanide at 0.5 and 1.0 mM inhibited the activity of the enzyme by about 20 and 61% respectively. The apparent Km value was calculated as 13.7 microM potassium ferricyanide and 4.3 microM NADH. 2. The Michaelis constants for cytochrome b5 and NADH were determined to be 1.67 and 7.7 microM from the Lineweaver-Burk plots. These results demonstrate that affinity of the lung reductase for its natural substrate is almost 10 times higher than that for potassium ferricyanide. 3. Addition of non-ionic detergent stimulated the rate of reductase-catalyzed reduction of lung cytochrome b5 up to 8.2-fold. 4. Kinetic studies performed with lung reductase by varying NADH and cytochrome b5 concentrations at different fixed concentrations at cytochrome b5 or NADH showed a series of parallel lines indicating a "ping-pong" type of kinetic mechanism for interaction of NADH and cytochrome b5 with lung cytochrome b5 reductase.

European Journal of Clinical Pharmacology, 1994

One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5... more One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5 mg coumarin p.o. after an overnight fast. Urine samples were collected before and 2, 4 and 8 h after drug administration. The extent and rate of formation of 7-OHcoumarin (7OHC) was determined by the urinary excretion of the metabolite as measured with the fluorometric method. On average, 80 % of 7OHC formed was excreted in 2 h. The total amount of 7OHC formed was 59.8 % (21.5 %) (mean and SD, n = 100, range 17-100 %) of the given dose. The percentage of 7OHC excreted during the first 2 h compared with the 7OHC excretion at 8 h was a constant and stable individual characteristic for the rate of the formation of 7OHC ('2 h coumarin test'). Although four individuals had relatively slow coumarin test values (34-40 %), no clear-cut polymorphism in the rate of 7OHC formation was found. However, 7OHC formation was lower in males and in cigarette smokers. Key words Coumarin, Coumarin 7-hydroxylation; interindividual variability, polymorphism Coumarin, a naturally occurring plant product, has been used clinically in postthrombotic syndromes, varicose insufficiency, and posttraumatic oedema [1]. Recently, the use of coumarin in the treatment of cancer and chronic brucellosis has also been reported [1, 2]. The scientific contents of this paper contribute to the goals of the COST B1 project.

Diabetes/Metabolism Research and Reviews, 2012

Background In diabetes mellitus, increased formation of reactive oxygen species due to high level... more Background In diabetes mellitus, increased formation of reactive oxygen species due to high level of glucose in both blood plasma and tissues creates oxidative stress and damages the tissues. Antioxidants together with the antioxidant enzymes are very important in order to protect the cells against oxidative damage. Methods Differential expressions of both mRNA and proteins of major antioxidant enzymes in streptozotocin-induced diabetic rat kidneys were measured with the help of real-time polymerase chain reaction and western blot analysis, respectively. Furthermore, effects of two strong antioxidants a-lipoic acid, vitamin C and their combination on the regulation of both expressions and the activities of antioxidant enzymes were also studied. Results In diabetic rat kidney tissue, both catalase and glutathione peroxidase activities were reduced (although mRNA expression for both was greatly increased) when compared with controls. No significant change was observed in superoxide dismutase (SOD) activity. Alpha-lipoic acid increased catalase activity towards the control values. Combined administration of alpha-lipoic acid and vitamin C increased the activities of both catalase and SOD, demonstrating a posttranslational effect. Glutathione concentrations were decreased in diabetic kidney; alpha-lipoic acid treatment partially restored the glutathione levels.

Studies in Organic Chemistry, 1998

A chitosan degrading fungus was isolated from chitosan and then identified as Penicillium spinulo... more A chitosan degrading fungus was isolated from chitosan and then identified as Penicillium spinulosum by the International Mycological Institute, England. The isolate was used for the production of chitosanase in a salts medium with either chitosan or Rhizopus cell walls as the sole carbon source. Chitosanase was produced under all the conditions tested, however better yields were obtained by using Rhizopus cell walls.

Toxicology in Vitro, 1995

The reduction of nitrofurantoin by purified liver nitrofurantoin reductase was followed by the pr... more The reduction of nitrofurantoin by purified liver nitrofurantoin reductase was followed by the production of superoxide radicals, which were detected by the reduction of epinephrine. The conditions for the formation of superoxide radicals were optimized. The maximum superoxide radical formation occurred at approximately 3.5 μg purified reductase, with optimum pH of 7.8 and at 0.05 mm nitrofuran- toin concentration. The

Archives of Toxicology, 1991

Treatment of rabbits with benzene (880 mg/kg/day), s.c. for 3 consecutive days, caused 3.8- and 5... more Treatment of rabbits with benzene (880 mg/kg/day), s.c. for 3 consecutive days, caused 3.8- and 5.7-fold increases in aniline 4-hydroxylation rates of liver and kidney microsomes, respectively. Benzene treatment markedly enhanced hydroxylation rats of p-nitrophenol by liver and kidney by 7.2- and 4.2-fold, respectively. Both of these enzymes are associated with cytochrome P-450 LM3a. In contrast, the activity of benzphetamine N-demethylase, associated with P-450 LM2, was not altered significantly in either liver or kidney microsomes. Although the total cytochrome P-450 contents of liver and kidney microsomes were not altered significantly by the benzene treatment, in the case of liver microsomes, formation of a new cytochrome P-450 with an apparent Mr of 51,400 was observed on SDS-PAGE. On the other hand, in the kidney microsomes, the intensity of the bands corresponding to approximate Mr of 50,000 and 51,400 was markedly increased. The results of the present work, in combination with those of the previous work (Arinç et al. 1988), indicate the existence of tissue specificity in the induction of rabbit P-450 isozyme by benzene.

European Journal of Clinical Pharmacology, 1994

One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5... more One hundred healthy Turkish volunteers (70 male, 30 female) aged from 19 to 56 years were given 5 mg coumarin p.o. after an overnight fast. Urine samples were collected before and 2, 4 and 8 h after drug administration. The extent and rate of formation of 7-OHcoumarin (7OHC) was determined by the urinary excretion of the metabolite as measured with the fluorometric method.