Involved in the regular timing (plastochron) of lateral organs formation. May regulate the rate of leaf initiation and the duration of vegetative phase. Seems to be redundant to the function of PLASTOCHRON1 and PLASTOCHRON2, but to act in an independent pathway. May be required for the synthesis of small signaling molecules that have a role in regulating meristem function. Involved in plant hormone homeostasis. Release of an unsubstituted, C-terminal glutamyl residue, typically from Ac-Asp-Glu or folylpoly-gamma-glutamates. Binds 2 Zn(2+) ions per subunit. Expressed in developing embryos, roots, leaf blade, vegetative shoot apex, inflorescence apex and flowers. Belongs to the peptidase M28 family. M28B subfamily. Intron retention.