Studies on the Mechanism of Action of the Copper(II) Enzyme, Galactose Oxidase

Mechanisms Whereby Mononuclear Copper Proteins Functionalize Organic Substrates

“…Galactose oxidase (GO) is a fungal protein, comprised of a single polypeptide chain (68 kDa) with one copper atom per active center [for reviews, see refs −131]. This enzyme catalyzes the two-electron oxidation of primary alcohols to aldehydes, which themselves can serve as substrates to yield carboxylic acids . In the course of a catalytic cycle, dioxygen becomes two-electron-reduced to hydrogen peroxide: Galactose oxidase shows a broad specificity, oxidizing low molecular weight alcohols such as d -galactose and dihydroxyacetone, as well as the non-reducing end of d -galactose bound to a polysaccharide chain. , Although the physiological function is not known for GO, it has been speculated to center on the production of hydrogen peroxide for use in lignin degradation…”

“…In an effort to explain the diamagnetic properties of active enzyme, two proposals had been put forth. The first invoked production of a Cu(III) species, while the second proposed a Cu(II) protein containing residual paramagnetic oxidant bound close enough to the metal center to permit spin coupling. , …”