We then examined the effect of an anti-oxidant, N-acetyl-l-cysteine (NAC), on motor performance and Aco2 activity in striatum of HD mice, and quantified the Aco2 level and activity in peripheral blood mononuclear cells (PBMC) of HD patients and pre-symptomatic HD mutation (PreHD) carriers. Here, ACO2 is linked to Huntington disease.