MPV17L is a mitochondrial inner membrane protein that functions as an atypical phosphodiesterase (PDE) regulating cyclic nucleotide metabolism 1. Despite lacking conserved PDE catalytic motifs, MPV17L exhibits genuine PDE activity and modulates cAMP/protein kinase A signaling pathways 2. The protein protects mitochondrial integrity through multiple mechanisms: it regulates reactive oxygen species (ROS) metabolism via antioxidant enzyme expression 3, directly activates the serine protease HtrA2 through PDZ domain interaction to inhibit mitochondrial superoxide generation and prevent apoptosis 4, and suppresses hydrogen peroxide biosynthesis while blocking mitochondrial outer membrane permeabilization 5. MPV17L exists in tissue-specific isoforms with differential ROS regulatory functions 6. Disease relevance includes diabetic kidney disease, where MPV17L is a novel downregulated hub gene 7, and chr16 obstructive pulmonary disease with asthma overlap, where promoter hypermethylation-mediated MPV17L downregulation correlates with increased ROS generation and apoptosis 8. MPV17L also serves as a prognostic biomarker in lung adenocarcinoma 9. Loss of MPV17L expression during oxidative renal injury 4 and miRNA-21-mediated repression in kidney fibrosis 10 highlight its clinical significance in renal pathology. Conversely, MPV17L knockout mice display improved glucose tolerance via Wnt/TGF-β pathway activation 2, suggesting potential therapeutic applications in metabolic diseases.