Metallocarboxypeptidase that mediates deglutamylation of tubulin and non-tubulin target proteins. Catalyzes the removal of polyglutamate side chains present on the gamma-carboxyl group of glutamate residues within the C-terminal tail of tubulin protein. Specifically cleaves tubulin long-side-chains, while it is not able to remove the branching point glutamate. Also catalyzes the removal of polyglutamate residues from the carboxy-terminus of non-tubulin proteins such as MYLK. May catalyze the hydrolysis of aspartate from the carboxy-terminus of target proteins. Does not show detyrosinase or deglycylase activities from the carboxy-terminus of target proteins. (L-glutamyl)(n+1)-gamma-L-glutamyl-L-glutamyl-[protein] + H2O = (L-glutamyl)(n)-gamma-L-glutamyl-L-glutamyl-[protein] + L-glutamate Binds 1 zinc ion per subunit. Belongs to the peptidase M14 family.