The Role of Self-Processing in Galactose Oxidase

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DESCRIPTION (provided by applicant): This project proposes to investigate the role of self-processing in the fungal protein, galactose oxidase. In the mature form, this enzyme possesses a modified tyrosine cofactor that plays a crucial role in the enzyme's ability to oxidize alcoholic substrates to their corresponding aldehydes. Biogenesis of the cofactor requires both copper and dioxygen and may be connected to another post-translational modification that results in cleavage of a 1.7 kDa pro-sequence from galactose oxidase. Crystal structures of galactose oxidase before and after self-processing reveal significant conformational changes that may influence the copper coordination sphere and its oxidation state. Dioxygen is proposed to act as an allosteric effector of pro-sequence cleavage, which in turn is responsible for a conformational change allowing biogenesis to occur. These suppositions can be tested by characterizing the products of self-processing and separately measuring the rates of both pro-sequence cleavage and cofactor biogenesis. Perturbations to self-processing through added reagents or mutagenesis will be used to identify potentially rate-determining steps and develop a comprehensive mechanism that links pro-sequence cleavage to cofactor biogenesis.