Oligopeptidase that may be involved in the degradation of proteasome-generated peptides (By similarity). 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. Up-regulated during senescence. Up-regulated by pathogen infection, elicitor treatment and flg22, a 22-amino acid sequence of the conserved N-terminal part of flagellin. No effect on germination. Belongs to the peptidase M3 family.