EpoY is an irreversible inhibitor of the major brain tubulin tyrosine carboxypeptidase (TCP), shown to be a complex of vasohibin-1 (VASH1) with the small vasohibin binding protein (SVBP). Reversible detyrosination of alpha-tubulin is vital to microtubule dynamics and functions including regulation of neuron differentiation, and defects in the detryosination have also been been associated with cancer and cardiomyopathies EpoY inhibited TCP activity with an IC50 value around 500 nM. It reduced detyrosinated a-tubulin levels and caused severe differentiation defects.