Toxic component of a type II toxin-antitoxin (TA) system. Acts as an endoribonuclease on single-strand RNA, cleaving between the second and third bases in the sequences CUCCU and UUCCU. Neutralized by coexpression with cognate antitoxin MazE2. Probably forms a complex with cognate antitoxin MazE2. Belongs to the PemK/MazF family.