Metallocarboxypeptidase that mediates protein 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. Mediates the deglutamylation of nucleotidyltransferase CGAS, leading to CGAS antiviral defense response activation (By similarity). Involved in KLF4 deglutamylation which promotes KLF4 proteasome-mediated degradation, thereby negatively regulating cell pluripotency maintenance and embryogenesis (PubMed:29593216). (L-glutamyl)(n+1)-gamma-L-glutamyl-L-glutamyl-[protein] + H2O = (L-glutamyl)(n)-gamma-L-glutamyl-L-glutamyl-[protein] + L-glutamate C-terminal L-alpha-aminoacyl-L-glutamyl-L-glutamyl-[tubulin] + H2O = C-terminal L-alpha-aminoacyl-L-glutamyl-[tubulin] + L-glutamate Binds 1 zinc ion per subunit. Interacts with MYLK. Colocalizes with gamma-tubulin in the centrioles at interphase and dividing cells and with glutamylated tubulin in basal bodies of ciliated cells. Belongs to the peptidase M14 family.