MAOB (monoamine oxidase B) is a mitochondrial enzyme that catalyzes the oxidative deamination of biogenic amines, producing hydrogen peroxide as a byproduct 1. While traditionally believed to degrade dopamine, recent evidence suggests MAOB primarily degrades other monoamines, with MAOA being the main dopamine-degrading enzyme 1. In Parkinson's disease, astrocytic MAOB contributes to pathology by producing excessive GABA and hydrogen peroxide in reactive astrocytes, leading to dopaminergic neuronal suppression and death 1. MAOB inhibitors like selegiline, rasagiline, and safinamide are established therapeutic agents for Parkinson's disease, reducing levodopa degradation and improving motor symptoms 2. Beyond neurodegeneration, MAOB exhibits context-dependent roles in cancer. In prostate cancer, stromal MAOB promotes tumor growth through reactive oxygen species production and CXCL12/CXCR4 signaling 3. Conversely, in clear cell renal cell carcinoma, MAOB acts as a tumor suppressor by inducing ROS-mediated DNA damage, p53 activation, and subsequent cell cycle arrest and apoptosis 4. MAOB expression is also regulated by DNA methylation patterns associated with various mental disorders 5. These findings highlight MAOB's diverse roles across different pathological contexts, making it an important therapeutic target in neurological diseases and cancer.