Models for the redox active site in galactose oxidase

Abstract

Modeling approaches have been used to develop insight into the nature of the redox active site of the free-radical-containing copper metalloenzyme galactose oxidase. The optical spectrum of the free radical generated by low-temperature UV irradiation of (methylthio)cresol is nearly identical to that observed for the free-radical site in metal-free apo galactose oxidase, supporting the assignment of the protein radical to a novel tyrosine-cysteine covalent cross-link structure recently reported from X-ray crystallographic studies. Basic characterization of the chemistry for this new type of biological redox group includes measurements of the substituent effects on phenolic proton acidic and observation of the oxygenation of (methylthio)cresol with peroxides