High Throughput Assessment of Gut Bacterial Tyrosine Decarboxylase Activity for Predicting Peripheral Levodopa Loss in Parkinson's Disease

Abstract Parkinson's disease (PD), a prevalent neurodegenerative disorder, is commonly managed through oral levodopa administration. However, the enzymatic activity of specific gut bacteria, particularly tyrosine decarboxylase (TDC), can metabolize levodopa, potentially leading to diminishing treatment effectiveness over time. Current methods for assessing TDC activity in PD patients focus mainly on genetic markers, lacking a robust and precise assay to measure gut bacterial TDC activity. Building upon prior research demonstrating levodopa conversion to dopamine using bacterial cultures and rat jejunum samples, we present an enhanced protocol to accurately quantify TDC activity in human fecal samples. This high-throughput approach employs fermentation reactions with fecal-derived bacteria, measuring TDC activity by converting supplemented levodopa to dopamine through Ultra-Performance Liquid Chromatography coupled with Electrochemical Detection (UPLC-ED). Serving as a predictive biomarker for levodopa loss, this method allows preparation of 96 fecal sample fermentation cultures within ~7 h. A single individual can conduct the protocol, with completion time varying based on factors such as sample size and time points collected.