Enzymatic activity of glucose oxidase covalently wired via viologen to electrically conductive polypyrrole films

The surface functionalization of an electrically conductive polypyrrole film (PPY) with a viologen, (N-(2-carboxyl-ethyl)-N'-(4-vinyl-benzyl)-4,4'-bipyridinium dichloride, or CVV) for the covalent immobilization of glucose oxidase (GOD) has been carried out. The viologen was first synthesized and graft polymerized on PPY film. It then served as an anchor via its carboxyl groups for the covalent immobilization of GOD. The surface composition of the as-functionalized substrates was characterized by X-ray photoelectron spectroscopy (XPS). The effects of the CVV monomer concentration on the CVV-graft polymer concentration and the amount of GOD immobilized on the surface were investigated. The activity of the immobilized GOD was compared with that of free GOD and the kinetic effects were also obtained. The cyclic voltammetric (CV) response of the GOD-functionalized PPY substrates was studied in a phosphate buffer solution under an argon atmosphere. The CV results support the mechanism in which CVV acts as a mediator to transfer electron between the electrode and enzyme, and hence regenerating the enzyme in the enzymatic reaction with glucose. High sensitivity and linear response of the enzyme electrode was observed with glucose concentration ranging from 0 to 20 mM.     

Glucose oxidase immobilized polyethylene-g-acrylic acid membrane for glucose oxidase sensor

A polyethylene-g-acrylic acid (PE-g-AA) graft copolymer was prepared via gamma-ray-irradiation-induced postirradiation procedures, and was used as support material for the immobilization of glucose oxidase. Soluble carbodiimides were used as the coupling agent. Reasonable yields were obtained with CMC but not with EDAC, EEDQ, or WRK. A number of factors were studied. (1) The use of water-soluble carbodiimides as condensing agent was attempted and the optimum condition for coupling glucose oxidase to PE-g-AA was established; (2) the effect of pH and temperature on the reactivity of native and immobilized glucose oxidase was studied. When exposed to temperatures in excess of 60 degrees C, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme. The optimum pH value for the performance of the enzyme-immobilized membrane was 5. 6. For 200 tests, the response error of glucose sensor was less than 4% and its linear detected range was 0-1000 ppm. The obtained glucose oxidase-immobilized PE-g-AA membranes were kept in pH 5. 6 acetate buffer solution at 4 degrees C. The glucose oxidase activity of the membrane was determined at sevenday intervals. The membranes still have 92% glucose oxidase activity even after eight weeks of storage.     

Immobilization of yeast pyridoxaminephosphate oxidase to halogenoacetyl polysaccharides

Pyridoxaminephosphate oxidase (EC 1.4.3.5, deaminating) that was partially purified about 40-fold from dry baker's yeast was immobilized to iodo- and bromoacetyl polysaccharides. The most effective carrier was an iodoacetyl cellulose, to which almost complete activity of pyridoxine 5'-phosphate oxidase was immobilized in 0.02M potassium phosphate buffer (pH 8.5) containing 2M ammonium sulfate at 4 degrees C. The immobilized enzyme was more stable than the purified, soluble enzyme against heat and pH change. It was confirmed that N-(5'-phosphopyridoxyl)-L-serine was degradedly oxidized to pyridoxal 5'-phosphate and L-serine by the immobilized enzyme as comparable rate as pyridoxine 5'-phosphate, whereas N-(5'-phosphopyridoxyl)-D-serine did not serve as substrate, as in the purified, soluble enzyme.     

Effect of enzyme-matrix composition on potentiometric response to glucose using glucose oxidase immobilized on platinum

Glucose oxidase (beta-D-glucose:oxygen 1-oxidoreductase, EC 1.1.3.4) was immobilized in a crosslinked matrix of bovine serum albumin, catalase, glucose oxidase and glutaraldehyde on platinum foil. When placed in glucose solution, this enzyme-electrode elicited a potentiometric response that varied with the changes in glucose concentration. The immobilized glucose oxidase was present at 7.4-10.1 micrograms enzyme protein/ml of matrix, as determined with 125I-labelled enzyme. The coupled enzyme activity was stable over 120 h; however, the apparent activity of the immobilized glucose oxidase was markedly less than that for the same amount of enzyme free in solution. This indicated a significant level of diffusional resistance within the enzyme-matrix. The potentiometric response to glucose increased significantly as either the thickness of the enzyme-matrix or the glutaraldehyde content was reduced; this also was attributed to diffusional effects. Several enzyme-electrodes, constructed without exogenous catalase and with different amounts of glucose oxidase, showed greater sensitivity in potentiometric response at low glucose oxidase loadings. These results are consistent with the hypothesis that the potentiometric response arises from an interfacial reaction involving a hydrogen peroxide redox couple at a platinum surface. The data also suggest that an optimum range of hydrogen peroxide concentration exists for maximum electrode sensitivity.     

Optimization of catechol production by membrane-immobilized polyphenol oxidase: a modeling approach

Although previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3-methylcatechol, 4-methylcatechol, catechol, and 4-chlorocatechol is demonstrated.     

Effects of immobilization on the kinetics of enzyme-catalyzed reactions. I. Glucose oxidase in a recirculation reactor system.

Glucose oxidase from Aspergillus niger was immobilized on nonporous glass beads by covalent bonding and its kinetics were studied in a packed-column recycle reactor. The optimum pH of the immobilized enzyme was the same as that of soluble enzyme; however, immobilized glucose oxidase showed a sharper pH-activity profile than that of the soluble enzyme. The kinetic behavior of immobilized glucose oxidase at optimum pH and 25 degrees C was similar to that of the soluble enzyme, but the immobilized material showed increased temperature sensitivity. Immobilized glucose oxidase showed no loss in activity on storage at 4 degrees C for nearly ten weeks. On continuous use for 60 hr, the immobilized enzyme showed about a 40% loss in activity but no change in the kinetic constant.     

Method of purification of glucose oxidase by means of affinity chromatography on immunoabsorbent]

The possibility to purify glucose oxidase from Penicillium vitale on immunosorbent containing specific antibodies to the enzyme covalently bound with Sepharose 4B is studied. The method of affinity chromatography was applied, beside routine methods of fractionating blood serum proteins, to isolate specific antibodies from antiserum of rabbits immunized with glucose oxidase. Immobilized on Sepharose glucose oxidase was used as biospecific sorbent. Specific antibodies to the enzyme were isolated using chromatograpy of gamma-globulins mixture followed by protein desorption from the column with 1 M NaC1 and 3% glucose. Antibodies were immobilized by their covalent binding to activated Sepharose. The immunosorbent obtained was used to purify low active preparation of glucose oxidase by means of affinity chromatography under conditions worked out for the antibodies isolation. The enzyme was eluted from the column with 1 M NaC1 (pH 3.0) containing 3% glucose. 5-Fold purified enzyme preparation was isolated.     

Immobilization of glucose oxidase on silica-based supports

Glucose oxidase (beta-D-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4) was covalently coupled to silica-based supports containing aldehyde functional groups. The activity of the immobilized enzyme was about 1000 U/g support. The optimum pH of the catalytic activity was 5.5 for the soluble enzyme and 6.0 for the immobilized enzyme. With glucose as a substrate the Km value of the immobilized enzyme was higher than in case of the soluble enzyme. The immobilized enzyme was found to be more thermostable than the soluble one. The immobilization did not affect the stability of glucose oxidase against the denaturing effect of urea.     

Purification and immobilization of rabbit liver aldehyde oxidase

Aldehyde oxidase (E.C. 1.2.3.1) was isolated from rabbit liver and two potential bioaffinity ligands, i.e., 3-aminocarbonyl-1-benzyl-6-methylpyridinium bromide and 3-aminocarbonyl-1-benzyl-4,6-dimethylpyridinium chloride, were tested for their applicability in a purification procedure for this enzyme. Various supports and different coupling methods were investigated for the immobilization of aldehyde oxidase. Adsorption to n-hexyl- and n-octylamine-substituted Sepharose 4B and DEAE Sepharose 6B gave the best retention of aldehyde oxidase activity. The storage stability of free enzyme and enzyme immobilized to n-octylamine-substituted Sepharose 4B was studied in several buffers at pH 7.8 and 9.0. This showed that the stability of immobilized enzyme was much less than that of free enzyme. The apparent operational stability of the immobilized enzyme preparation, however, improved substantially compared to soluble enzyme, although the corresponding product yield is still very poor. Coimmobilization of catalase and/or superoxide dismutase provided no significant increase of the apparent operational stability and product yield. A positive effect on both parameters was found for aldehyde oxidase-n-alkylamine Sepharose 4B preparations by increasing the amount of enzyme adsorbed per unit weight of support, whereas the productivity of these preparations remained about constant.     

Immobilization of glucose oxidase on sepharose by UV-initiated graft copolymerization

The performance of a new method of enzyme immobilization based on photochemically initiated direct graft copolymerization was recently investigated. The immobilization reaction can be carried out in a simple way and by carefully selecting the reaction conditions, the enzyme-graft copolymer can be obtained as the main reaction product. Coupling efficiency of glucose oxidase has been found to depend only on the amount of photocatalyst (FeCl(3)) fixed on Sepharose used as polysaccharide support. Small quantities of glycidymethacrylate (GMA) (0.25 g/g dry Sepharose) are sufficient but necessary to achieve the best enzyme coupling efficiency (20-40%). Enzyme immobilization occurs very rapidly and the entire reaction occurs within 60 min. Reaction patterns and physicochemical characteristics of the obtained enzyme-graft copolymers exclude the glucose oxidase entrapment: therefore a covalent attachment mechanism may be proposed. The kinetic parameters of immobilized glucose oxidase (K(m)' = 2.0 x 10(-2)M) are quite similar to those of free enzyme (K(m) = 1.93 x 10(-2)M), and no diffusion limitation phenomena are evidenced in samples having different enzyme or polymer content. Lyophilization, thermostability, and long-term continuous operation also have been investigated. The advantages of this method over that using vinylenzyme copolymerization are discussed.     

Pulmonary xanthine oxidase activity of rats exposed to prolonged immobilization stress

This study was designed to study xanthine oxidase (XO) and xanthine dehydrogenase (XD) activity in the lung of rats exposed to prolonged restraining immobilization stress. Immobilization caused more than twofold increase of xanthine oxidase activity in the rat lung. The activity of xanthine oxidase decreased in lung homogenates incubated at -20 degrees C for 24 h. The same incubation of homogenates from control rats caused a non-significant increase of the activity. No measurable NAD(+)-dependent xanthine dehydrogenase activity could be established in the lungs of both control rats and rats subjected to immobilization. All rats revealed methylene blue-dependent xanthine dehydrogenase activity which was more than two-times higher in the immobilized animals. Incubation at -20 degrees C for 24 h increased the methylene blue-dependent xanthine dehydrogenase activity in homogenates from control rats and decreased the enzyme activity in homogenates from immobilized rats. A working hypothesis was proposed for the sequence of events explaining the results obtained: XO-catalyzed generation of activated oxygen species may take place in the initiation of lipid peroxidation in the lung of rats immobilized for prolonged periods of time.     

Effect of alpha-methylation on inactivation of monoamine oxidase by N-cyclopropylbenzylamine

Monoamine oxidase (MAO) was shown previously [Silverman, R. B., & Hoffman, S. J. (1980) J. Am. Chem. Soc. 102, 7126-7128] to catalyze the oxidation of N-cyclopropylbenzylamine (N-CBA) at two sites on the molecule. Oxidation at the benzyl methylene gave benzaldehyde and cyclopropylamine; oxidation of the cyclopropyl group, which involved cyclopropyl ring cleavage, led to inactivation of the enzyme. In this paper it is shown that methylation of the benzyl methylene dramatically alters this partition ratio in favor of enzyme inactivation. Contrary to a previous report [Alles, G., & Heegaard, E. V. (1943) J. Biol. Chem. 147, 487-503], it is shown here that alpha-methylbenzylamine is a substrate for MAO; consequently, N-cyclopropyl-alpha-methylbenzylamine (N-C alpha MBA) is a good candidate for mechanism-based inactivation. N-Cyclopropyl[7-14C]benzylamine, N-cyclopropyl-alpha-methyl[phenyl-14C]benzylamine, N-[1-3H]-cyclopropylbenzylamine, and N-[1-3H]cyclopropyl-alpha-methylbenzylamine are synthesized, and product formation following MAO inactivation is quantified. The results obtained with these compounds indicate that with N-C alpha MBA, alpha-methylbenzyl oxidation (which produces acetophenone and cyclopropylamine) is only 1% that of cyclopropyl oxidation (which gives enzyme inactivation), whereas with N-CBA the amount of oxidation at the corresponding sites is equal. It also is shown that the Ki values for (R)-(+)- and (S)-(-)-alpha-methylbenzylamine are similar, suggesting that dimethylation of N-CBA should not interfere with binding to MAO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Properties of a glucose oxidase covalently immobilized on amorphous AlPO4 support

Glucose oxidase (GOD) was covalently immobilized on amorphous AlPO₄ as well as on an AlPO₄/clay mineral Sepiolite system. Immobilization of the enzyme was carried out through the -amino group of lysine residues through an aromatic Schiff's-base. Activation of the support was obtained after reaction of appropriate molecules with support surface –OH groups. The enzymatic activities of native, and different immobilized GOD systems and filtrates, were followed by the amount of liberated -gluconic acid obtained in the enzymatic β- -glucose oxidation with the aid of an automatic titrator. The kinetic properties of native and immobilized GOD were obtained for glucose concentrations in the range of physiological conditions and at different working conditions such as reaction temperature, reaction pH, and enzyme concentration.

The binding percentage of enzymes was in the 50–80% range, with residual and specific activities in the 65–80% and 90–150% ranges, respectively. No change in the pH optimum and only slight changes in the V_max and K_M kinetic parameters with respect to native GOD were observed, so that not only was little deactivation of enzyme obtained throughout the immobilization process but also that the stability of the covalently bound enzyme in the two supports appeared to have increased with respect to the soluble enzyme. GOD immobilization also increased its efficiency and operational stability in repeated uses on increasing the amount of immobilized enzyme.     

Immobilization of glucose oxidase in conducting graft copolymers and determination of glucose amount in orange juices with enzyme electrodes

Glucose oxidase was immobilized in conducting copolymers of three different types of poly(methyl methacrylate-co-thienyl methacrylate). Immobilization of enzyme was carried out by the entrapment in conducting polymers during electrochemical polymerization of pyrrole on the copolymer electrodes. Maximum reaction rate, Michaelis-Menten constants, temperature, pH and operational stabilities were determined for immobilized enzyme. The amount of glucose in orange juices of Turkey was investigated by using enzyme electrodes.     

Preparation of some immobilized linked enzyme systems and their use in the automated determination of disaccharides

1. Glucose oxidase (EC 1.1.3.4), amyloglucosidase (EC 3.2.1.3), invertase (EC 3.2.1.26) and beta-galactosidase (EC 3.2.1.23) were covalently attached via glutaraldehyde to the inside surface of nylon tube. 2. The linked enzyme system, comprising invertase immobilized within a nylon tube acting in series with glucose oxidase immobilized in a similar way, was used for the automated determination of sucrose. 3. The linked enzyme system, comprising beta-galactosidase immobilized within a nylon tube acting in series with glucose oxidase immobilized in a similar way, was used for the automated determination of lactose. 4. The linked enzyme system, comprising amyloglucosidase immobilized within a nylon tube acting in series with glucose oxidase immobilized in a similar way, was used for the automated determination of maltose. 5. Mixtures of glucose oxidase and amyloglucosidase were immobilized within the same piece of nylon tube and used for the automated determination of maltose. 6. Mixtures of glucose oxidase and invertase were immobilized within the same piece of nylon tube and used for the automated determination of sucrose.     

Glucose oxidase immobilization on a novel cellulose acetate-polymethylmethacrylate membrane

Glucose oxidase (GOD) was immobilized on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane. The immobilized GOD showed better performance as compared to the free enzyme in terms of thermal stability retaining 46% of the original activity at 70 degrees C where the original activity corresponded to that obtained at 20 degrees C. FT-IR and SEM were employed to study the membrane morphology and structure after treatment at 70 degrees C. The pH profile of the immobilized and the free enzyme was found to be similar. A 2.4-fold increase in Km value was observed after immobilization whereas Vmax value was lower for the immobilized GOD. Immobilized glucose oxidase showed improved operational stability by maintaining 33% of the initial activity after 35 cycles of repeated use and was found to retain 94% of activity after 1 month storage period. Improved resistance against urea denaturation was achieved and the immobilized glucose oxidase retained 50% of the activity without urea in the presence of 5M urea whereas free enzyme retained only 8% activity.     

15N- and 13C-NMR investigations of glucose oxidase from Aspergillus niger

The apoprotein of glucose oxidase from Aspergillus niger was reconstituted with specifically 15N- and 13C-enriched FAD derivatives and investigated by 15N- and 13C-NMR spectroscopy. On the basis of the 15N-NMR results it is suggested that, in the oxidized state of glucose oxidase, hydrogen bonds are formed to the N(3) and N(5) positions of the isoalloxazine system. The hydrogen bond to N(3) is more pronounced than that to N(5) as compared with the respective hydrogen bonds formed between FMN and water. The resonance position of N(10) indicates a small decrease in sp2 hybridization compared to free flavin in water. Apparently the isoalloxazine ring is not planar at this position in glucose oxidase. Additional hydrogen bonds at the carbonyl groups of the oxidized enzyme-bound FAD were derived from the 13C-NMR results. A strong downfield shift observed for the C(4a) resonance may be ascribed in part to the decrease in sp2 hybridization at the N(10) position and to the polarization of the carbonyl groups at C(2) and C(4). The polarization of the isoalloxazine ring in glucose oxidase is more similar to FMN in water than to that of tetraacetyl-riboflavin in apolar solvents. In the reduced enzyme the N(1) position is anionic at pH 5.6. The pKa is shifted to lower pH values by at least 1 owing to the interaction of the FAD with the apoprotein. As in the oxidized state of the enzyme, a hydrogen bond is also formed at the N(3) position of the reduced flavin. The N(5) and N(10) resonances of the enzyme-bound reduced FAD indicate a decrease in the sp2 character of these atoms as compared with that of reduced FMN in aqueous solution. Some of the 15N- and 13C-resonance positions of the enzyme-bound reduced cofactor are markedly pH-dependent. The pH dependence of the N(5) and C(10a) resonances indicates a decrease in sp2 hybridization of the N(5) atom with increasing pH of the enzyme solution.     

葡萄糖氧化酶的有机相共价固定化

将葡萄糖氧化酶(GOD)在最适pH条件下冻干后,以戊二醛活化的壳聚糖为载体,分别在传统水相和1,4-二氧六环、乙醚、乙醇三种不同的有机相中进行共价固定化。通过比较水相固定化酶和有机相固定化酶的酶比活力、酶学性质及酶动力学参数,考察酶在有机相中的刚性特质对酶在共价固定化过程中保持酶活力的影响。结果表明,戊二醛浓度为0.1%、加酶量为80 mg/1 g载体、含水1.6%的1,4-二氧六环有机相固定化GOD与水相共价固定化GOD相比,酶比活力提高2.9倍,有效酶活回收率提高3倍;在连续使用7次后,1,4-二氧六环有机相固定化GOD的酶活力仍为相应水相固定化酶的3倍。在酶动力学参数方面,不论是表观米氏常数,最大反应速度还是转换数,1,4-二氧六环有机相固定化的GOD(Kmapp=5.63 mmol/L,Vmax=1.70μmol/(min.mgGOD),Kcat=0.304 s-1)都优于水相共价固定化GOD(Kmapp=7.33 mmol/L,Vmax=1.02μmol/(min.mg GOD),Kcat=0.221 s-1)。因此,相比于传统水相,GOD在合适的有机相中进行共价固定化可以获得具有更高酶活力和更优催化性质的固定化酶。该发现可能为酶蛋白在共价固定化时因构象改变而丢失生物活性的问题提供解决途径。     

Affinity chromatography of putrescine oxidase from Micrococcus rubens and spermidine dehydrogenase from Serratia marcescens.

Putrescine oxidase [EC 1.4.3.4], putrescine : oxygen oxidoreductase (deaminating) (flavin-containing), from Micrococcus rubens and spermidine dehydrogenase from Serratia marcescens were adsorbed on amine-Sepharose 4B in which one of the terminal amino groups of diamine or triamine was covalently bound to Sepharose 4B leaving the other terminal amino group(s) free. The affinities of these enzymes for the amine-Sepharose 4B increased on increasing the chain length of the methylene groups in the immobilized amines and fell upon addition of the substrate. The affinity of putrescine oxidase modified with 1-ethyl-3-(3-dimethylamino-propyl)-carbodiimide (EDC) was reduced in comparison with that of the native enzyme so far as 1,12-diaminododecane-Sepharose 4B was concerned. From these results, it can be concluded that the interactions between the enzyme and the amine-Sepharose result from specific affinities mediated through the active sites of the enzymes. It is suggested that spermidine dehydrogenase as well as putrescine oxidase has as anionic point and a hydrophobic region in the active site. On the basis of these results, the applicability of the enzyme affinities to purification procedures was examined. When partially purified enzymes were subjected to affinity chromatography, the following results were obtained. Putrescine oxidase gave a purification factor of 40-fold with about 100% recovery on a 1,12-diaminododecane-Sepharose column. In the case of spermidine dehydrogenase, the purification factor and recovery on a 1,8-diaminooctane-Sepharose column were about 1,200-fold and 86%, respectively. By introducing affinity chromatography as a purification step, each enzyme could be purified more simply and with higher recovery.