PANK2 and pantothenate kinase-associated neurodegeneration: In addition, cysteine is a substrate of the PANK2 enzyme and may play a key role in iron accumulation, therefore in PKAN patients, there is an increase of cysteine and chelate leading to the accumulation of iron in the brain.[11,12] It is thought that excessive accumulation of cysteine in the globus pallidus region results in decreasing pantothenate, causing iron chelation and oxidative damage to basal ganglia.