Detyrosination
Detyrosination is a form of posttranslational modification that occurs on alpha-tubulin. It consists of the removal of the C-terminal tyrosine to expose a glutamate at the newly formed C-terminus. Tubulin polymers, called microtubules, that contain detyrosinated alpha-tubulin are usually referred to as Glu-microtubules while unmodified polymers are called Tyr-microtubules.
The tubulin carboxypeptidases that cleave the terminal tyrosine are two proteases called vashohibins, in complex with a small protein SVBP that acts as stabilising chaperon. The detyrosynating activity was first identified in the late 1970s. It is a slow acting enzyme that uses polymeric tubulin as a substrate. As a result, only stabilized microtubules accumulate this particular modification. Tubulin detyrosination is reversed by the tubulin-tyrosine ligase, which acts only on alpha-tubulin monomer. Since the majority of microtubules are very dynamic, they do not contain much detyrosinated tubulin.
