A RAPID ANTEROGRADE AXONAL-TRANSPORT OF CARBOXYPEPTIDASE-H IN RAT SCIATIC-NERVES

Using the highly sensitive HPLC-fluorophotometry technique, anterograd e and retrograde axonal transport of carboxypeptidase H (CPH), a putat ive prohormone processing enzyme that removes a basic amino acid from the C-terminus of a precursor peptide, was measured 12-72 h after doub le ligations of rat sciatic nerves. CPH-like activity in rat sciatic n erves was 60-fold lower than that in the pituitary gland. CPH-like enz yme activity was rapidly accumulated in the proximal segment and peake d 48 h after ligation. The axonal flow was 100 mm/day, indicating that CPH in rat sciatic nerves is rapidly transported to the nerve termina ls as an active form. The properties of the enzyme were similar to tho se of CPH in the brain: The pH optimum is at 5.5, and the molecular ma ss is similar to 50 kDa. These results suggest that active CPH in the PNS is transported by a rapid anterograde axonal flow and may play a r ole in converting proneuropeptides to active neuropeptides under the a xonal transport.