PTOX (plastid terminal oxidase) is a component of electron transfer chain responsible for desaturation of phytoene, which prevents the generation of reactive oxygen species. It is involved in the differentiation of plastids: chloroplasts, amyloplasts, and etioplasts. PTOX is expressed ubiquitously in plant tissues and is located in the lumen.Synonymes: IM, IM1, immutants, AOX4, alternative oxidase 4, ubiquinol oxidase 4, chloroplastic/chromoplastic