Methanethiol oxidase

SELENBP1 encodes methanethiol oxidase (MTO), a selenium-binding protein that catalyzes the oxidation of methanethiol, an organosulfur compound produced by gut bacteria (UniProt: Q13228). The enzyme may also function in sensing reactive xenobiotics and potentially in intra-Golgi protein transport. MTO deficiency causes extraoral halitosis due to methanethiol oxidase deficiency (EHMTO), an autosomal recessive condition marked by accumulation of sulfur-containing metabolites and characteristic cabbage-like breath odor.

In Alzheimer's disease, SELENBP1 is upregulated in post-mortem AD brain tissue compared to age-matched controls (mean log2 fold-change: 0.6154), as measured by quantitative proteomics across subcellular fractions (Chaparral AD proteomics). The biological significance of elevated MTO in AD pathology remains to be determined, though increased oxidative stress responses and metabolic dysregulation are hallmarks of neurodegeneration.