CYP27C1 is a mitochondrial cytochrome P450 monooxygenase that catalyzes the 3,4-desaturation of all-trans-retinol (vitamin A1) to all-trans-3,4-didehydroretinol (vitamin A2), with lower efficiency toward retinal and retinoic acid substrates 1. This enzymatic conversion is critical for spectral tuning of visual pigments; knockout of cyp27c1 in zebrafish eliminates vitamin A2 production and abolishes the organism's ability to red-shift photoreceptor sensitivity and perceive near-infrared light 1. The enzyme functions via a two-protein mitochondrial electron transfer system involving FDXR and FDX1/FDX2. Beyond vision, CYP27C1 expression levels influence lung cancer tumorigenicity and drug sensitivity; CYP27C1 knockdown enhances cell proliferation, migration, and tolerance to anticancer agents through dysregulation of the IGF-1R/Akt/p53 signaling pathway 2. Genome-wide association studies identified CYP27C1 variants associated with plasma protein C levels and ischaemic heart disease risk in African American populations 34. CYP27C1 expression has been associated with avascular necrosis of the femoral head, particularly in idiopathic cases 5. These findings suggest CYP27C1 has pleiotropic functions spanning vision, cancer biology, and cardiovascular physiology.