The development and application of an engineered direct electron transfer enzyme for continuous levodopa monitoring

Levodopa, the primary treatment for Parkinson’s Disease, has a narrow therapeutic window further complicated by the lack of real-time feedback, primarily due to the absence of an enzyme specific to levodopa. We addressed this by developing a novel direct electron transfer type (DET) enzyme, copper dehydrogenase (CoDH), engineered from an extremophile derived multicopper oxidase (MCO), for use in a continuous levodopa sensor. By introducing mutations into the type 2 and type 3 copper ligand histidine residues, the enzyme drastically decreased its oxidase activity while enhancing DET activity with the electrode. Using this developed CoDH, a chronoamperometric levodopa sensor was constructed, which was minimally affected by environmental changes, or by interferents, including levodopa metabolites, adjunct medications, and common plasma and interstitial fluid components. A miniaturized levodopa sensor was constructed and was able to detect levodopa as low as 138 nM, suggesting its future application for in vivo subcutaneous measurement. The multicopper oxidase protein from Pyrobaculum aerophilum (McoP) was mutated, yielding copper dehydrogenase (CoDH). CoDH was then utilized to prepare a levodopa sensor across the entire physiologically relevant levodopa range.