Enhances the tyrosine carboxypeptidase activity of vash1 and vash2, thereby promoting the removal of the C-terminal tyrosine residue of alpha-tubulin. Also required to enhance the solubility and secretion of vash1 and vash2. May play a role in axon and excitatory synapse formation (By similarity). Detected both intracellularly and extracellularly. Within cells, localizes mainly to the apical part of the cell. Belongs to the SVBP family.