Role of the copper in galactose oxidase

Abstract

Galactose oxidase is a metalloenzyme containing a single copper atom per molecule. The mechanism of action of galactose oxidase is studied in this paper by investigating substrate specificity and activation by peroxidase, and probing the copper site by electron spin resonance (ESR) spectroscopy. Line-shape simulation of ESR spectra are also reported and a comparison is made between observed and simulated spectra for galactose oxidase. A comparison is also reported for the enzyme from various commercial sources and enzyme isolated from a fungus in this laboratory. The results of this investigation suggest that the copper is in an environment of four in-plane nitrogens with axial symmetry.

A dual staining method for identifying mucins of different gastric epithelial mucous cells

“…Since galactose oxidase preferentially oxidizes terminal or internally linked penultimate ~-galactose or ~-N-acetylgalactosamine (Cleveland et al, 1975;Goudsmit et al, 1984), these results indicate that sugar residues responsible for the GOCTS reactivity involve at least J3-N-acetylgalactosamine in the secretor cells and J3-Nacetylgalactosamine and ~-galactose in the nonsecretor cells. Thus, in the human stomach, these cells exhibited galactose oxidase-labile reactivities for N-acetylgalactosamine-specific lectins in the secretor cells of blood group determinants and for both N-acetylgalactosamine-and galactose-specific lectins in the non-secretor cells.…”

Direct electron transfer between copper-containing proteins and electrodes

“…The active form of the enzyme-GalOD ox has been reported to react with GalOD red with quantitative formation of GalOD semi (Wright and Sykes, 2001b). Activation of GalOD was also observed in the presence of peroxidase, but not using other iron-heme proteins such as catalase or ferricytochrome c (Cleveland et al, 1975). It seems that not only small redox molecules, but also proteins can modulate the activity of GalOD, most probably via a direct protein-protein interaction.…”

ESR of Copper in Biological Systems

“…The mechanism of action of galactose oxidase has been investigated by Cleveland et al (1975) from the point of view of (1) the specificity of the enzyme toward the substrate, (2) the activation of the enzyme by peroxidase, and (3) the nature of the copper site by ESR. The ESR spectrum of fungal galactose oxidase has been interpreted in terms of rhombic symmetry.…”

“…The ESR spectrum of fungal galactose oxidase has been interpreted in terms of rhombic symmetry. Computer simulations by Cleveland et al (1975) using Kosman's parameters do not fit the experimental spectrum. A much better fit can be obtained by using axial symmetry with splittings by four nitrogen atoms.…”