Galactose oxidase/catalase

Carbohydrate, phosphate buffer, galactose oxidase, catalase, temperature, CUSO4,... 

By application of EMMA Regehr and Regnier developed several assays for enzymes that produce (galactose oxidase and glucose oxidase) or consume (catalase) hydrogen peroxide. Unlabeled enzymes were determined in the femto-mole mass range, while detection limits of less than 10,000 molecules were reported for catalase [101]. 

Scheme 4.14 L-Fructose synthesis starting from glycerol and DHAP using a multi-enzyme system with galactose oxidase, Rhal PA, catalase and APase.

Galactose oxidase of P. circinatus was apparently inhibited by traces of BESOD. It can be inactivated by H Oj produced in the reaction unless catalase was added. There was an activation by traces of O J. In the absence of oxidants the reaction usually showed an induction period The enzyme, used at very low concentrations in the assays, was protected by proteins like serumalbumin. SOD did, however, not alter the reaction rate when added after 15 min This was interpreted by an inactivation of SOD by the H O accumulated in the reaction but it could just as well mean that SOD had no effect on the active enzyme, but that it did lower the activation in the induction period. Peroxidase activated galactose oxidase and suppressed the effect of SOD It did protect the enzyme against H O inactivation and could have been responsible for appreciable amounts of OJ, produced from O and from radicals formed in its action on a substrate. 

Treatment with galactose oxidase. Oxidation of myelin with galactose oxidase was performed as described previously for similar oxidation of rat spinal cord preparations (4). Typically, myelin containing 0.2-1.1 mg protein is incubated with 100-500 units of galactose oxidase in 1-3 ml of phosphate buffer (10-100 mM, pH 7.2-7.4) with or without catalase. After the incubation at room temperature to 30°C for the duration of 30 min to overnight, myelin is recovered by centrifugation, washed, and lyophilized. Total lipids were extracted from the dried residue and the oxidized cerebroside as well as unaltered cerebrosides were analyzed as described above. Alternatively, the incubation was stopped by the addition of 5 volumes of chloroform/methanol (2/1, v/v) and mixed. The lower layer after centrifugation of the mixture is washed and then evaporated to dryness, and the total lipids obtained were analyzed as described above. 

Scheme 6. Preparation of pentasaccharide 11 [42] (a) galactose oxidase Dactylium dendroides), catalase (bovine liver), phosphate buffer, 37 °C (b) 5-(2-aminoethylamino)-l-naphthalene-sulfonate (EDANS), MeOH, reflux, then NaBHjCN...

Fig. 4.18 Automatic enzymatic determination of D-galactose in serum in a continuous FIA system with liquid dialysis for the removal of interfering macromolecules. Reactors Cu2t, Bond-Elut-NHz-Cu Cat, catalase GalOD, galactose oxidase POD, peroxidase. Absorbent arylamino porous glass. (Reproduced from [14] with permission of Elsevier).

Figure 6.3 Cascade reaction for the chemo-enzymatic synthesis of biotinylated UDP-Cal and UDP-GalNAc. (a) UDP-Glc(NAc)-4 -epimerase, (b) galactose oxidase, (c) catalase, (d)...

In a further pioneering work reported by Schoevaart and Kieboom [43], which also represents one of the first examples for the combination of a biotransformation with subsequent chemocatalytic steps, a galactose oxidase was utilized for an initial oxidation of methyl-D-galactoside 42 with molecular oxygen in the additional presence of a catalase (Scheme 19.15). Notably, then two further steps were conducted that were based on an organocatalytic dehydration (with proline) and a subsequent... 

Figure 2. Oxidation of low molecular weight guar gum (5% w/v) monitored in bottles with an OxiTop measuring head at pH 7 and room temperature with galactose oxidase (GO) in the presence or absence of Horse Radish Peroxidase (HRP) and Catalase (CAT).

Donnelly 13) describes the use of galactose oxidase in combination with catalase for the oxidation of guar gum to produce products with various viscosities or gels under mild conditions for food applications. Oxidized guar gum and locust bean gum can also be used as precursors for various chemically modified polysaccharides. Yalpani and Hall exploited the aldehyde functionality to attach various functional groups via reductive amination, oxidation, and reduction 14), Oxidized guar can also be further oxidized chemically to obtain a... 

Kelleher and Bhavanandan showed that raffinose was partly converted to 6"-carboxyraffinose when treated with galactose oxidase and catalase 16). More recently it was shown that UDP-galactose could be oxidized to UDP-GalA with a yield of more than 95% in the presence of high levels of galactose oxidase and catalase, at prolonged incubation times (77). 

Several metabolites found in food samples have been estimated using the thermometric approach. These include glucose, cellobiose, lactose, maltose, galactose, lactate, oxalate, phopholipids, ascorbic acid, ethanol, urea [18], xanthine and hypoxanthine [41,42]. Glucose was estimated by co-immobilizing glucose oxidase and catalase [43]. The presence of catalase doubled the thermal... 

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