The AGTPBP1 gene, also known as CCP1, encodes a zinc carboxypeptidase enzyme that is responsible for catalysing the deglutamylation of target proteins. CCP1 can carry out the deglutamylation of polyglutamate side chains added by post-translational modification to the C-termini of tubulin proteins. It can also mediate the deglutamylation of gene-encoded polyglutamates from proteins such as MYLK.
Mouse models have helped elucidate the physiological role of CCP1. The mouse orthologue gene, Ccp1, is found to be mutated in the Purkinje cell degeneration (pcd) phenotype of mice. These pcd mice exhibit ataxia subsequent to cerebellar Purkinje cell degeneration. They also suffer the progressive deterioration of thalamic neurons, retinal photoreceptors and olfactory bulb mitral cells. Analysis of pcd mice has shown increased levels of tubulin polyglutamylation in the brain.