[6] Variations in human MT-ND5 are associated with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) as well as some symptoms of Leigh's syndrome and Leber's hereditary optic neuropathy (LHON).

[6] The MT-ND5 product is a subunit of the respiratory chain Complex I that is supposed to belong to the minimal assembly of core proteins required to catalyze NADH dehydrogenation and electron transfer to ubiquinone (coenzyme Q10).

[11] Initially, NADH binds to Complex I and transfers two electrons to the isoalloxazine ring of the flavin mononucleotide (FMN) prosthetic arm to form FMNH2.

[6] A small percentage of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) are caused by a G>A mutation at base pair 13513 in the MT-ND5 gene.

[12] Those with MT-ND5 mutations can display the major features of MELAS and MERRF in some patients, as well as symptoms of Leigh's syndrome and/or Leber's hereditary optic neuropathy (LHON) in others.