Involved in peroxisome biogenesis and the import of peroxisomal matrix proteins that contain the peroxisomal targeting sequence PTS2. Required for peroxisomal targeting of PEX7 and growth on oleate. Acts as an activator of the seryl-tRNA synthetase SES1 by increasing its binding to tRNA. Interacts with PEX7, PEX13 and SES1. Belongs to the peroxin-21 family.