Galactose oxidase binding

I-Labeled Galactose Oxidase Binding to Myelin... 

The function of the metal site in the oxygen-dependent radical enzymes galactose oxidase, amine oxidases, ribonucleotide reductase, and cytochrome c oxidase is inter alia to bind 02 in their reduced forms and undergo the appropriate redox chemistry to generate a metal-bound, activated oxygen species of variable nature. 

However, the Schiff base complex lacks the stability towards reduction by CN" that characterizes the Cu( II) in galactose oxidase. While the enzyme binds a single CN" even at large CN" excess (22), the Cu(II) in the model is reduced by the ligand. To assess the underlying structural components which stabilize the enzymic Cu(II) towards reduction by CN", a five-coordinate model (Figure 2) having square bipyramidal symmetry was prepared (23). (The conditions and system procedures... 

Galactose Oxidase Optical Transitions and Anion Binding... 

It is interesting to consider the effect of exogenous ligands (which have previously been shown to bind to the Cu(II) atom inner sphere by ESR studies (22)) on the optical spectrum of galactose oxidase. (While... 

All anions which bind to the Cu(II) in galactose oxidase lower the gzz and Azz values (22). This is consistent with (but not required for) a blue shift in the d-d transitions (32, 33, 34). Fe(CN)63" is the only anion among the limited ones we have studied which produces a red shift in the optical bands (Figure 4). At 1 1, 5 1, or 100 1 molar ratios of Fe(CN)63" to enzyme the same difference absorbance spectrum is obtained, and it is consistent with complex formation between galactose oxidase and the anion. Namely, the positive difference peaks at 455, 830,... 

Fig. 7. Inner sphere of the galactose oxidase copper-binding site. Geometric details of the ligand arrangement in the aquo complex are indicated in the figure. (Based on protein coordinates PDB ID IGOG.)...

Fig. 21. Proposed catalytic mechanism for substrate oxidation by galactose oxidase. (A) Substrate binding displaces Tyr-495 phenolate which serves as a general base for abstracting the hydroxylic proton. (B) Stererospecihc pro- hydrogen abstraction by the Tyr-Cys phenoxyl radical. (C) Inner sphere electron transfer reducing Cu(II) to Cu(I). (D) Dissociation of the aldehyde product.

Chemically binding enzymes to nylon net is very simple and gives strong mechanically resistant membranes (135). The nylon net is first activated by methylation and then quickly treated with lysine. Finally, the enzyme is chemically bound with GA. The immobilized disks are fixed direcdy to the sensor surface or stored in a phosphate buffer. GOD, ascorbate oxidase, cholesterol oxidase, galactose oxidase, urease, alcohol oxidase (135), and lactate oxidase (142) have been immobilized by this procedure and the respective enzyme electrode performance has been established. 

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