It is of interest whether the CatB inhibitory activity of CysC is also involved in its neuroprotective activity, because the previous reports have shown that CatB is activated in ALS pathology23,24 and involved in motor neuronal degeneration.25 First, we confirmed the activation of CatB in the mutant SOD1 model. Here, SOD1 is linked to amyotrophic lateral sclerosis.