Exploring dopa decarboxylase as an ideal biomarker in Parkinson's disease with focus on regulatory mechanisms, cofactor influences, and metabolic implications.

Parkinson's disease (PD), the most common motor neurodegenerative disorder, lacks a reliable biomarker for early detection. Elevated dopa decarboxylase (DDC) levels show promise as a biomarker for PD, distinguishing it from other neurodegenerative diseases, such as Alzheimer's disease (AD). This perspective explores DDC's regulatory mechanisms, its specificity to PD, and the influence of cofactors like pyridoxal-5-phosphate, tyrosine, and thyroxine on its activity, addressing a critical question: why does elevated DDC not increase dopamine, serotonin, or norepinephrine levels?