Oligopeptidase degrading short peptides from 8 to 23 amino acid residues. Plays a role in the degradation of transit peptides and of peptides derived from other proteolytic events. Does not exhibit a strict cleavage pattern. Binds salicylic acid. Hydrolysis of oligopeptides, with broad specificity. Gly or Ala commonly occur as P1 or P1' residues, but more distant residues are also important, as is shown by the fact that Z-Gly-Pro-Gly-|-Gly-Pro-Ala is cleaved, but not Z-(Gly)(5). Binds 1 zinc ion. Inhibited by salicylic acid. Down-regulated during senescence. Not regulated by pathogen infection, elicitor treatment and flg22, a 22-amino acid sequence of the conserved N-terminal part of flagellin. No visible phenotype and no effect on germination; probably due to the presence of the presequence proteases PREP1 and PREP2. Belongs to the peptidase M3 family. Extended N-terminus.