Mitochondrial-targeted catalase (mCAT) has a negative effect on ROS levels, and overexpression of mCAT might therefore be beneficial in diminishing the negative effects of ROS on health and lifespan. This study on th effects of mCAT on teh proteome shows that overexpression of mCAT in early life might actually not be beneficial.
http://onlinelibrary.wiley.com/doi/10.1111/acel.12472/full (free full text)