Simultaneous co-immobilization of glucose oxidase and catalase in their substrates

Glucose oxidase (GOD) and catalase (CAT) were simultaneously co-immobilized onto magnesium silicate (Florisil®) by covalent coupling. Glucose was added in immobilization mixture and hydrogen peroxide, which is the substrate of CAT, was produced in coupling mixture during immobilization time. Therefore, co-immobilization of GOD and CAT was carried out in the presence of both their substrates: glucose and hydrogen peroxide, respectively. The effect of glucose concentration in immobilization mixture on activities of GOD and CAT of co-immobilized samples were investigated. Maximum GOD and CAT activities were determined for samples co-immobilized in the presence of 15 and 20 mM glucose, respectively. Co-immobilization of GOD and CAT in the presence of their substrates highly improved the activity and reusability of both enzymes. © 2007 Pleiades Publishing, Inc.Devlet Planlama Örgütü: 2003 K 320 120-G, FBE.2002ACKNOWLEDGMENTS This work was supported by the Turkish State Planning Organization (DPT), project 2003 K 320 120-G, and Research Grants FBE.2002.D 219 from Cukurova University

Immobilization and kinetics of catalase onto magnesium silicate

Bovine liver catalase was immobilized covalently with glutaraldehyde, or glutaraldehyde+3-aminopropionic acid as a spacer, onto magnesium silicate. The coupling time was determined as 2h for immobilization. The pH and temperature optima as well as the changes in the kinetics (Km, Vmax, Ea) of the immobilized catalase was observed and discussed. Immobilized catalase preparations showed higher storage stabilities than free catalase. The half-life of free catalase, catalase immobilized via glutaraldehyde and catalase immobilized via glutaraldehyde+spacer were calculated as 2, 55 and 10 days at room temperature and 4, 85 and 107 days at 5°C, respectively. The operational stability of the catalase immobilized via glutaraldehyde was higher than the catalase immobilized via glutaraldehyde+spacer. The remaining activity of the catalase immobilized via glutaraldehyde was about 90% and that of the catalase immobilized via glutaraldeyde+spacer was about 30% after 20 cycles of batch operation. © 2003 Elsevier Ltd. All rights reserved.This work was supported by Research Grants FBE YL 113 from Cukurova University

The changes of erythrocyte membrane Na+-K+ ATPase activities in subjects with normal and impaired glucose tolerance

The effects of glucose on Na+-K+ ATPase activity of erythrocyte membranes were investigated under in vitro and in vivo conditions. Results of the study, in vitro, showed that Na+-K+ ATPase activity of erythrocyte membrane was increased by increasing glucose concentrations (0-30 mM). When glucose-6-phosphate (0-100 mM) was used instead of glucose no significant change occurred in Na+-K+ ATPase activity. Tunicamycin (0.01 ng/ml) when added to the incubation media together with glucose prevented the increase in Na+-K+ ATPase activity

Effects of ozone on the activity of erythrocyte membrane Na+-K+ ATPase

PubMedID: 7804127Ozone (5 µmol.min-1) inhibited the human erythrocyte membrane Na+-K+ ATPase (EC.3.6.1.39) activity in a time dependent manner. Inhibition was more pronounced for the first 5 min of ozone exposure in the directly ozon exposed membranes than in the membranes prepared from ozone exposed erythrocytes. However, Na+-K+ ATPase activities of both preparations were inhibited to the same extent (about 70%) at the end of 10 min ozone exposure. It was also determined that there was a close relationship between the decrease of enzyme activity and the increase in the thiobarbituric acid reactive substances in both types of preparations. Na+-K+ ATPase was inhibited by ozone even at the presence of vitamin E or vitamin C. However, the degree of the inhibitions and the amounts of thiobarbituric acid reactive products formed were smaller than the corresponding values found in the absence of these vitamins

Activity and storage stability of immobilized glucose oxidase onto magnesium silicate

Glucose oxidase (GOD) was covalently immobilized onto florisil (magnesium silicate) carrier via glutaraldehyde. Immobilization conditions were optimized: the amount of initial GOD per grams of carrier as 5 mg, pH as 5.5, immobilization time as 120 min and temperature as 10°C. Under the optimized reaction conditions activities of free and immobilized GOD were measured. Free and immobilized GOD samples were characterized with their kinetic parameters, and thermal and storage stabilities. KM and Vmax values were 68.2mM and 435 U mg GOD-1 for free and 259 mM and 217 U mg GOD-1 for immobilized enzymes, respectively. Operational stability of the immobilized enzyme was also determined by using a stirred batch type column reactor. Immobilized GOD was retained 40% of its initial activity after 50 reuses. Storage stabilities of the immobilized GOD samples stored in the mediums with different relative humidity in the range of 0-100% were investigated during 2 months. The highest storage stability was determined for the samples stored in the medium of 60% relative humidity. Increased relative humidity from 0% to 60% caused increased storage stability of immobilized GODs, however, further increase in relative humidity from 80% to 100% caused a significant decrease in storage stability of samples. © 2005 Elsevier B.V. All rights reserved.Devlet Planlama Örgütü: 2003 K 320 120-G, FBE.2002This work was supported by Turkish State Planning Organization (DPT) project 2003 K 320 120-G and Research Grants FBE.2002.D 219 from Cukurova University

Protein-coated microcrystals of Prunus armeniaca hydroxynitrile lyase: an effective and recyclable biocatalyst for synthesis of (R)-mandelonitrile

In this study, the crude solution of Prunus armeniaca hydroxynitrile lyase (ParsHNL) was simultaneously precipitated onto K2SO4 salt in acetone to immobilize ParsHNL as protein-coated microcrystals and the obtained preparations (PCMCs-ParsHNL) were used for the synthesis of (R)-mandelonitrile in buffer-saturated methyl tert-butyl ether (pH 4.0). The yield and enantiopurity of (R)-mandelonitrile were 100 and 90.5%, respectively, for free HNL, whereas the corresponding yield and enantiopurity values were 100 and 99.8%, respectively, for PCMCs-ParsHNL after 96 h reaction time. The free HNL and PCMCs-ParsHNL were stored at room temperature and 5 °C during 30 days and the results showed that PCMCs-ParsHNL had better storage stability compared to the free HNL at both room temperature and 5 °C. PCMCs-ParsHNL was imaged by a scanning electron microscopy and PCMCs-ParsHNL was rectangular in shape. PCMCs-ParsHNL was recycled five times in the synthesis of (R)-mandelonitrile and 75.2% initial activity recovery and 99.8% enantiomeric excess for (R)-mandelonitrile was determined after five uses. Thus, immobilizing ParsHNL as PCMCs provided highly active and reusable HNL preparations for (R)-mandelonitrile synthesis in buffer-saturated methyl tert-butyl ether. © 2018, Institute of Chemistry, Slovak Academy of Sciences.Firat University Scientific Research Projects Management Unit: FBA-2015-5067Acknowledgements The financial support was provided by Scientific Research Projects Unit of Cukurova University with the project number of FBA-2015-5067

The effect of lead on sera malonyldialdehyde, vitamin C, vitamin E and erythrocyte reduced glutathione

Lead is one of the heavy metals that is toxic for human and animals. Several reports indicate that peroxidation damage of tissues in laboratory animals are enhanced in acute toxicity from transition metal ions such as copper, iron, mercury and lead. In this study sera malondialdehyde (MDA), erythrocyte reduced glutathione(GSH), sero vitamin C and E values were determined in 30 male subjects occupationally exposed to lead 20 healthy male subjects were used as control group. Blood lead level of control group was found as 10 ± 1.8 mg/dL. However, blood lead level of lead exposed subjects was very high with a value of 317 ± 47 mg/dL. MDA, GSH, vitamin C and vitamin E levels of lead exposed subjects were 0.56 ± 0.30 nmol/mL, 2.77 ± 0.50 mmol/g Hb, 1.33 ± 0.40 mg/dL and 5.40 ± 0.60 mg/mL, respectively. MDA, GSH, vitamin C and vitamin E value of control group were 0.17 ± 0.02 nmol/mL, 5.10 ± 1.20 mmol/g Hb, 1.75 ± 0.34 mg/dl and 8.98 ± 1.75 mg/mL, respectively. Our experimental results showed that there is a significant increase in MDA values of lead exposed subjects as compared with that of the controls. However, vitamin E, vitamin C and GSH values of lead exposed subjects were significantly lower than the vitamin E, vitamin C and GSH values of normal controls

Improvement of activity and stability of Rhizomucor miehei lipase by immobilization on nanoporous aluminium oxide and potassium sulfate microcrystals and their applications in the synthesis of aroma esters

In this study, Rhizomucor miehei lipase (RML) was immobilized on the hexagonally-ordered nanoporous aluminium oxide membranes (RML-Al 2 O 3 -NP) by adsorption and as protein-coated microcrystals (RML-PCMCs) by simultaneously precipitating RML on micron-sized potassium sulfate crystals (K 2 SO 4 ) in pre-chilled acetone. The hydrolytic activities of immobilized lipase preparations were investigated in terms of p-nitrophenyl palmitate hydrolysis and their esterification activities were examined for the synthesis of some aroma esters such as butyl acetate, isoamyl acetate, hexyl acetate, heptyl acetate, and geranyl acetate. The immobilization yields were 33.8 and 25.1%, respectively for RML immobilized on Al 2 O 3 -NP membranes and potassium sulfate crystals. The catalytic efficiency ratios of RML-Al 2 O 3 -NP and RML-PCMCs were 2.3- and 3.9-fold higher than that of the free lipase, respectively in terms of hydrolytic activity. The free lipase was stabilized as 4.1- and 10.5-fold, respectively at 40 and 50 °C when immobilized on Al 2 O 3 -NP. The corresponding stabilization factors were 4.6- and 12.8-fold higher for RML-PCMCs. RML-Al 2 O 3 -NP and RML-PCMCs maintained 84 and 86% of their initial hydrolytic activities, respectively after 10 reuses. Of the synthesized aroma esters, the highest yield was obtained for the geranyl acetate. After 4 h reaction time, no geraniol was detected in the preparative-scale (196 g/L) synthesis of geranyl acetate for both the immobilized lipases when the initial geraniol amount, vinyl acetate amount, RML-PCMCs amount, and reaction temperature values were 1 mmol, 3 mmol, 100 mg (or 300 mg RML-Al 2 O 3 -NP), and 50 °C, respectively. These results show that the immobilization of R. miehei lipase by adsorption on nanoporous aluminium oxide and as protein-coated microcrystals leads to the obtention of highly stable, catalytically more active, and reusable lipase preparations. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Firat University Scientific Research Projects Management Unit: FBA-2017-9317, FBA-2015-4934This work was supported from Scientific Research Projects of Cukurova University with the projects number of FBA-2015-4934 and FBA-2017-9317. The authors are thankful to the Cukurova University research fund for their financial support