Enzymatic detyrosination of tubulin tyrosinated in rat brain slices and extracts

Tubulin was tyrosinated in slices and in extracts of brain of rats of 3, 25, and 120 days of age by successive incorporation of [14C]tyrosine and [3H]tyrosine, respectively. The release of the incorporated amino acid was measured by using tubulinyl-tyrosine carboxypeptidase, carboxypeptidase A, and tubulin-tyrosine ligase. With the carboxypeptidases no differences in either the rates or the extents of the release of tyrosine between these two differently labeled tubulins were found. Differences were found when the detyrosination was catalyzed by the ligase and these were attributed to a higher inactivation of tubulin labeled in slices than of that labeled in extracts.