Adsorption, desorption, and activity of glucose oxidase on selected clay species.

The adsorption of the enzyme glucose oxidase (EC 1.1.3.4) to clays followed the pattern described for other proteins as being pH dependent. Maximum adsorption occurred at or below the isoelectric point of the enzyme. The amount of enzyme adsorbed to clay was influenced by the type of clay used, and also the saturating cations. Initially adsorbed enzyme showed low specific activities, and as amounts of enzyme adsorbed approached maximum stauration of clay, specific activities increased approaching that determined for free enzyme. The adsorption of glucose oxidase involved a temperature-independent cation-exchange mechanism, and enzyme adsorbed to surfaces of clay could be desorbed in active form by elevation of pH of suspending solution. This was followed by a slower temperature-dependent fixation, probably by hydrogen bonding, which resulted in protein being irreversibly adsorbed to clay surfaces. It is proposed that on adsorption of glucose oxidase to clay surfaces unravelling of the protein structure occurred, which allowed penetration of protein into the interlamellar spaces of montmorillonite. This proposal was based on the observed expansion of montmorillonite to 23 A, and the decreases in amount of a second-protein lysozyme adsorbed with extended incubation times of glucose oxidase - clay complexes at pH 4.5.     

Spectroscopic properties of spinach catalase

Spinach catalase (hydrogen-peroxide: hydrogen-peroxide oxidoreductase, EC 1.11.1.6) has been purified to homogeneity. The purified enzyme has a specific activity of 25 000 units per mg protein. The presence of 2-mercaptoethanol and phenylmethylsulfonyl fluoride (PMSF) were required for high yields of the enzyme. The molecular weight of the enzyme was estimated to be 125 000 by gel filtration. Subunit analysis by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed a single peptide with M_r 55 000. The enzyme, which exhibits optical absorbance maxima at 279, 403, 542, 592 and 723 nm and shoulders at 290, 500 and 630 nm, contains 2 mol iron per mol protein. One of the two irons can be attributed to protoheme, while the other iron appears to be present in a novel heme. The oxidized catalase exhibited two sets of high-spin, ferriheme EPR signals.     

The interrelationship of superoxide dismutase and peroxidatic enzymes in the red cell.

Activities of superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) and catalase (hydrogen-peroxide:hydrogen-peroxide oxidoreductase, EC 1.11.1.6) were determined during the course of incubation of red cell suspensions with 1,4-naphthoquinone-2-sulfonic acid. In the absence of glucose, incubation with napthoquinone sulfonate resulted in an inhibition of catalase and superoxide dismutase. The catalase inhibitor, 3-amino-1,2,4-triazole enhanced inactivation of catalase in the presence of naphthoquinone sulfonate and this in turn led to augmented inhibition of superoxide dismutase. The presence of glucose in the incubation medium prevented napthoquinone sulfonate-induced enzyme inhibition in the absence of aminotriazole, but had little effect in the presence of aminotriazole. The relevance of these findings to the cellular interrelationship of peroxidatic enzymes and superoxide dismutase is discussed.     

Partition of catalase and its peroxidase activities in human red cell membrane: effect of ATP depletion.

Partititon of catalase (hydrogen-peroxide:hydrogen-peroxide oxidoreductase EC 1.11.1.6) and peroxidase (donor:hydrogen-peroxide oxidoreductase EC 1.11.1.7) activities between the red cell membrane and the cytosol were studied under various experimental conditions. A small but significant amount of catalase (1.6%) was retained on human red cell membranes prepared by hemolysing washed red cells with 30 volumes of 10 mM Tris buffer, pH 7.4. Membrane -bound catalase had a relatively higher peroxidase activity than the soluble enzyme fraction. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate of the solubilized membranes demonstrated catalase to be a single band with a molecular weight of 60 000. Membranes prepared from adenosine triphosphate-depleted red cells depicted a two to three-fold increase in catalase activity, as well as an increase in 60 000 molecular weight band on polyacrylamide gel electrophoresis. The extra amount of retained catalase was a less efficient peroxidase than found in fresh membranes. The binding of catalase to ATP-depleted red cell membranes was dependent upon both pH and hemolysing ratio. Red cells incubated at pH 7.1 demonstrated a decrease in bound catalase, as did membranes prepared from red cells hemolysed at 1:100 dilution. beta-Mercaptoethanol decreased the catalase activity in the membranes and increased the odianisidine peroxidase activity without any significant effect on the 60 000-dalton band.     

Immunoaffinity layering of enzymes

A general procedure for the high yield immobilization of enzymes with the help of specific anti-enzyme antibodies is described. Polyclonal antibodies were raised against Aspergillus niger glucose oxidase and horseradish peroxidase in rabbits and the gamma globulin (IgG) fraction from the immune sera isolated by ammonium sulphate fractionation followed by ion-exchange chromatography. Immobilization of glucose oxidase and horseradish peroxidase was achieved by initially binding the enzymes to a Sepharose matrix coupled with IgG isolated from anti-(glucose oxidase) and anti-(horseradish peroxidase) sera, respectively. This was followed by alternate incubation with the IgG and the enzyme to assemble layers of enzyme and antibody on the support. The immunoaffinity-layered preparations obtained thus were highly active and, after six binding cycles, the amount of enzyme immobilized could be raised about 25 times over that bound initially. It was also possible to assemble layers of glucose oxidase using unfractionated antiserum in place of the IgG. The bioaffinity-layered preparations of glucose oxidase and horseradish peroxidase exhibited good enzyme activities and improved resistance to heat-induced inactivation. The sensitivity of a flow injection analysis system for measuring glucose and hydrogen peroxide could be remarkably improved using immunoaffinity-layered glucose oxidase and horseradish peroxidase. For the detection of glucose, a Clark-type oxygen electrode, constructed as a small flow-through cell integrated with a cartridge bearing immunoaffinity-layered glucose oxidase was employed. The hydrogen peroxide concentration was analysed spectrophotometrically using a flow-through cell and the layered horseradish peroxidase packed into a cartridge. The immunoaffinity-layered enzymes could be conveniently solubilized at acid pH and fresh enzyme loaded onto the support. Immunoaffinity-layered glucose oxidase was successfully used for the on-line monitoring of the glucose concentration during the cultivation of Streptomyces cerevisiae. Received: 16 November 1998 / Received revision: 22 March 1999 / Accepted: 26 March 1999     

Quartz Sand as an Adsorbent for Purification of Extracellular Glucose Oxidase from Penicillium funiculosum 46.1

A procedure for purification of extracellular glucose oxidase (GO, EC 1.1.3.4) from a filtrate of culture liquid (CLF) of the fungus Penicillium funiculosum 46.1 has been developed using alluvial quartz sand as an adsorbent. Modifying the sand by changing the charge and polarity did not lead to a significant increase in its adsorption capacity towards GO. The effectiveness of sand and aluminum oxide used as adsorbents for GO isolation from CLF has been compared. Glucose oxidase isolated from CLF by adsorption on sand exhibited a greater catalytic activity than enzyme preparations obtained by column chromatography on CLF. Glucose oxidase from P. funiculosum 46.1 was adsorbed on sand more effectively than on aluminum oxide. It is concluded that sand may be used for fractionation of partially purified GO.     

Quartz sand as an adsorbent for purification of extracellular glucose oxidase from Penicillium funiculosum 46.1

The procedure of purification of extracellular glucose oxidase (GO, EC 1.1.3.4) from culture-liquid filtrate (CLF) of the fungus Penicillum funiculosum 46.1 using alluvial quartz sand as an adsorbent has been developed. The modification of sand by changing the charge and polarity did not lead to a significant increase in its adsorption capacity towards GO. The effectiveness of sand and aluminum oxide, used as sorbents for isolation of GO from CLF, was compared. Glucose oxidase, isolated from CLF by adsorption on sand, exhibited a greater catalytic activity compared to the enzyme specimens obtained by column chromatography on CLF. Sand adsorbed GO from P. funiculosum 46.1 more effectively than aluminum oxide. It is concluded that sand may be used for fractionation of partly purified GO.     

The binding of a fluorescent activator 2-(N-decyl)aminonaphthalene-6-sulfonic acid to pyruvate oxidase

E. coli pyruvate oxidase (pyruvate:ferricytochrome b1 oxidoreductase, EC 1.2.2.2) is a peripheral membrane flavoenzyme which has been purified to homogeneity. In vivo the oxidase resides on the inner surface of the cytoplasmic membrane and is coupled to the bacterial electron transport chain. In vitro, the purified oxidase requires lipids for full enzymatic activity. Previous studies have characterized the conformational and energetic coupling between the lipid-binding site(s) and the catalytic active site. The affinity of the enzyme for phospholipids and detergents is significantly enhanced when the flavoprotein is in the reduced form, i.e., in the presence of pyruvate and the required cofactor, thiamin pyrophosphate. The lipid-binding studies were hindered due to the complicating factor of the self-association of the substrate-reduced flavoprotein. In this paper, fluorescence techniques are employed to measure the binding of a detergent-like activator to the oxidase. The experiments are performed at much lower protein concentrations than previously employed, so that protein aggregation is not a problem. The chromophore on the activator, 2-(N-decyl)aminonaphthalene-6-sulfonic acid is effective at quenching the pyruvate oxidase intrinsic tryptophan fluorescence. Quenching titrations are used to obtain the binding isotherm. AT DNS concentrations less than 10(-5) M, the results show a larger amount of DNS binding to the reduced flavoprotein than to the oxidized form of the enzyme. This is the concentration range where DNS is an effective activator of the enzyme. This represents a class of binding sites specifically found on pyruvate oxidase and not apparent in other proteins such as lysozyme or aldolase. At the DNS concentration which is optimum for activation approx. 20 molecules of DNS are bound per enzyme tetramer in the absence of the substrate. The pyruvate-reduced form of the enzyme binds about 40--50 molecules of DNS per tetramer. Qualitatively, the results are similar to what was previously found for both sodium dodecyl sulfate and cetyl trimethylammonium bromide. However, in both these cases, the amount of bound detergent was nearly an order of magnitude less than the values obtained using DNS.     

Mediation of glycosylated and partially-deglycosylated glucose oxidase of Aspergillus niger by a ferrocene-derivatised detergent.

A ferrocene-derivatised detergent, (11-ferrocenylundecyl) trimethylammonium bromide (FTMAB), when oxidised to the corresponding ferricinium ion, was found by electrochemical studies to be an effective electron acceptor for reduced glucose oxidase of Aspergillus niger (EC 1.13.4) and thus acts as a electron-transfer mediator between glucose oxidase and a working electrode held at a potential sufficiently positive to reoxidise reduced FTMAB. An increase in mediating activity was produced when FTMAB was present in concentrations above its critical micelle concentration. An 'enzyme electrode' was formed by adsorption of glucose oxidase and FTMAB surfactant on a graphite rod. The electrode functioned as an amperometric biosensor for glucose in phosphate-buffered saline solution. A mixed micelle of glucose oxidase and FTMAB, probably adsorbed on the electrode surface, appears to be advantageous for the amperometric determination of glucose. Additionally, glucose oxidase was treated with alpha-mannosidase. When this partially-deglycosylated glucose oxidase was incorporated in an enzyme electrode, a 100-fold increase in the second-order rate constant (k) for electron transfer between the enzyme and FTMAB was observed, together with increased current densities, with respect to the equivalent values for FTMAB and commercial glucose oxidase. The use of deglycosylated enzymes in biosensors is suggested.     

Adsorption kinetics of laterally and polarly flagellated Vibrio.

The adsorption of laterally and polarly flagellated bacteria to chitin was measured, and from the data obtained, a modified Langmuir adsorption isotherm was derived. Results indicated that the adsorption of laterally flagellated Vibrio parahaemolyticus follows the Langmuir adsorption isotherm, a type of adsorption referred to as surface saturation kinetics, when conditions are favorable for the production of lateral flagella. When conditions were not favorable for the production of lateral flagella, bacterial adsorption did not follow the Langmuir adsorption isotherm; instead, proportional adsorption kinetics were observed. The adsorption of some polarly flagellated bacteria exhibited surface saturation kinetics. However, the binding index (the product of the number of binding sites and bacterial affinity to the surface) of polarly flagellated bacteria differed significantly from that of laterally flagellated bacteria, suggesting that polarly flagellated bacteria adsorb to chitin by a different mechanism from that used by the laterally flagellated bacteria. From the results of dual-label adsorption competition experiments, in which polarly flagellated V. cholerae competed with increasing concentrations of laterally flagellated V. parahaemolyticus, it was observed that laterally flagellated bacteria inhibited the adsorption of polarly flagellated bacteria. In contrast, polarly flagellated bacteria enhanced the adsorption of V. cholerae. In competition experiments, where V. parahaemolyticus competed against increasing concentrations of other bacteria, polarly flagellated bacteria enhanced V. parahaemolyticus adsorption significantly, whereas laterally flagellated bacteria only slightly enhanced the process. The direct correlation observed between surface saturation kinetics, the production of lateral flagella, and the ability of laterally flagellated bacteria to inhibit the adsorption of polarly flagellated bacteria suggests that lateral flagella represent a component of bacterial structure that is important in the adsorption of laterally flagellated bacteria to surfaces. A model for adsorption events of laterally flagellated bacteria is proposed, based on the evidence presented.     

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.     

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.     

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.     

Steady-state kinetics of yeast cytochrome c peroxidase catalyzed oxidation of inorganic reductants by hydrogen peroxide

Rates of yeast cytochrome c peroxidase (ferrocytochrome c:hydrogen-peroxide oxidoreductase, EC 1.11.1.5) catalyzed oxidation of bis(tripyridine)cobalt(II) ion, penta(amine)pyridineruthenium(II) ion and ferrocyanide ion by hydrogen peroxide have been found to obey the empirical equation: (formula; see text) in the pH range 5 to 8, and at saturating H2O2 concentrations. [( S] and [CcP] are the concentrations of the reductant and the enzyme, respectively.) Values of k2 were found to be independent of the reductant. The term k0[S] is only significant with the cobalt and ruthenium complexes at high pH. The mechanism proposed to account for this rate equation differs significantly from previous mechanistic proposals. In particular, the rate data require the assignment of the rate-limiting step at high substrate concentrations to a slow electron-transfer within the enzyme, and not, as previously suggested, to saturation of substrate binding to the enzyme. Also, the term k0[S] implies that the reactive substrates, including the natural substrate (yeast cytochrome c), react with the hydrogen peroxide-heme complex and not with the radical species formed by reaction with hydrogen peroxide in the absence of reductants.     

Use of a bioelectrochemical cell for the synthesis of (bio)chemicals

A bioelectrochemical cell containing either d-glucose oxidase (β-d-glucose:oxygen 1-oxidoreductase, EC 1.1.3.4) or xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) plus dichlorophenol-indophenol as electron acceptor in one half-cell, and chloroperoxidase (chloride:hydrogen-peroxide oxidoreductase, EC 1.11.1.10) in the other half-cell is described. Due to a combination of chemical, biochemical and electrochemical reactions, electricity and specific (bio)chemicals can be produced in the cell simultaneously and in both compartments. Furthermore, the oxidases in a bioelectrochemical cell are not inactivated by H₂O₂ and as a result the operational lifetimes of the oxidases were increased about five-fold.     

Studies on the mechanism of inhibition of redox enzymes by substituted hydroxamic acids.

Substituted primary hydroxamic acids were found to inhibit the catalytic activity of a number of redox enzymes. The inhibition was not related to the nature of the metal-active site of the enzyme nor to the nature of the oxygen-containing substrate. Two easily available enzymes, mushroom tyrosinase (monophenol,dihydroyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) and horseradish peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7), which were potently inhibited by hydroxamic acids, were chosen for more detailed study. A kinetic analysis of the inhibitory effects on the partially purified tyrosinase of mushroom (Agaricus bispora) revealed that inhibition was reversible and competiitive with respect to reducing substrate concentration, but was not competitive with respect to molecular oxygen concentration. A spectrophotometric and EPR study of the binding of salicylhydroxamic acid to horseradish peroxidase revealed that his hydroxamic acid was bound to the enzyme in the same manner as a typical substrate, hydroquinone. Spectroscopic and thermodynamic measurements of the binding reactions suggested that this binding site is close, to but, not directly onto, the heme group of the enzyme. From these results it is concluded that the mode of inhibition of hydroxamic acid need not be, as generally supposed, by metal chelation, and mechanisms involving either hydrogen bonding at the reducing substrate binding site or the formation of a charge transfer complex between hydroxamic acid and an electron-accepting group in the enzyme are considered to be more feasible. The relevance of these findings to deductions on the nature of other hydroxamic acid-inhibitable systems is discussed.     

Hydrophobic interactions of cytochrome c oxidase. Application to the purification of the enzyme from rat liver mitochondria.

The binding of rat liver cytochrome c oxidase to phenyl-Sepharose and various alkyl and omega-aminoalkyl agarose gels has been studied. Deoxycholate-solubilized cytochrome c oxidase was tightly bound to hexyl, octyl, omega-aminohexyl, omega-aminooctyl agarose as well as to phenyl-Sepharose. This hydrophobic interaction was used for the purification of cytochrome c oxidase. The enzyme which was eluted from phenyl-Sepharose was devoid of NADH (NADPH)-acceptor reductase activities. The heme a content was 15.4 nmol per mg of protein. The purified enzyme was resolved into seven polypeptides upon polyacrylamide gel electrophoresis in sodium dodecylsulfate with molecular weights of 40,000, 23,200, 21,500, 14,500, 12,600, 8900, and 4900. Antibodies raised in rabbits against the pure enzyme did not cross-react with cytochrome c oxidases from either beef heart or yeast mitochondria. Cytochrome c oxidase bound to octyl-Sepharose or phenyl-Sepharose exhibited a very low catalytic activity. The possible modes of interaction of cytochrome c oxidase with the hydrophobic ligands are discussed.     

Application of the reaction of dithioesters with epsilon-amino groups in lysine to the chemical modification of proteins

The reaction of lysine with dithioesters was applied to horseradish peroxidase donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7) using carboxymethyl dithiotridecanoate: three to four lysine residues were modified. The modified enzyme was soluble and active in diethyl ether. Papain (EC 3.4.22.2) was modified with carboxymethyl dithiobenzoate: two lysine residues were modified. The modified enzyme was soluble and active in dimethylsulfoxide. From these results it is concluded that dithioesters are efficient reagents for the modification of peripheral lysine residues of proteins. Aromatic dithioesters, less reactive but more selective, should be recommended for thiol-dependent enzymes such as papain.     

Application of the reaction of dithioesters with ε-amino groups in lysine to the chemical modification of proteins

The reaction of lysine with dithioesters was applied to horseradish peroxidase donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7) using car☐ymethyl dithiotridecanoate: three to four lysine residues were modified. The modified enzyme was soluble and active in diethyl ether. Papain (EC 3.4.22.2) was modified with car☐ymethyl dithiobenzoate: two lysine residues were modified. The modified enzyme was soluble and active in dimethylsulfoxide. From these results it is concluded that dithioesters are efficient reagents for the modification of peripheral lysine residues of proteins. Aromatic dithioesters, less reactive but more selective, should be recommended for thiol-dependent enzymes such as papain.     

Rates of cyanide binding to the catalytic intermediates of mammalian cytochrome c oxidase, and the effects of cytochrome c and poly(L-lysine).

Rate constants of cyanide binding to 'fast' oxidase have been measured in the fully-oxidised (O), peroxy (P) and ferryl (F) states at pH 8.0. Values of 2.2, 8 and 10 M-1 s-1, respectively, were obtained. Thus, none of these states appears to exhibit a rate that would identify it as the species responsible for the extremely rapid cyanide binding observed during turnover. On the other hand, with 'oxidised' enzyme as prepared, containing a very small fraction of one-electron-reduced (E state) oxidase, a corresponding fraction of enzyme exhibited spectral changes consistent with cyanide binding with a rate constant in excess of 10(4) M-1 s-1. Evidence is presented suggesting that mediation of electron transfer from one-electron-reduced, cyanide-liganded enzyme to free, ferric oxidase, rather than a global protein conformational change of the enzyme, is responsible for the greatly enhanced cyanide binding rates seen in the presence of cytochrome c or poly(L-lysine). Inter-oxidase electron exchange in 'oxidised' enzyme can result in a complicated dependence of the binding rate on cyanide concentration. We have demonstrated that this may give rise to a saturation of the rate of cyanide binding.