A family of carboxypeptidases catalyzing - and -tubulin tail processing and deglutamylation

Tubulin posttranslational modifications represent an important mechanism involved in the regulation of microtubule functions. The most widespread among them are detyrosination, alpha increment 2-tubulin, and polyglutamylation. Here, we describe a family of tubulin-modifying enzymes composed of two closely related proteins, KIAA0895L and KIAA0895, which have tubulin metallocarboxypeptidase activity and thus were termed TMCP1 and TMCP2, respectively. We show that TMCP1 (also known as MATCAP) acts as alpha-tubulin detyrosinase that also catalyzes alpha Delta 2-tubulin. In contrast, TMCP2 preferentially modifies beta I-tubulin by removing three amino acids from its C terminus, generating previously unknown beta I Delta 3 modification. We show that beta I Delta 3-tubulin is mostly found on centrioles and mitotic spindles and in cilia. Moreover, we demonstrate that TMCPs also remove posttranslational polyglutamylation and thus act as tubulin deglutamylases. Together, our study describes the identification and comprehensive biochemical analysis of a previously unknown type of tubulin-modifying enzymes involved in the processing of alpha- and beta-tubulin C-terminal tails and deglutamylation.