Proteolysis of peripheral nerve myelin in acute experimental allergic neuritis

Proteolysis of peripheral nerve myelin was studied in rats with experimental allergic neuritis (EAN). In vitro measurements using rat sciatic nerve homogenate and denatured bovine myelin as a substrate showed two myelin specific enzyme activities at pH 3.8 (inhibited by pepstatin) and pH 5.8 (inhibited by PMSF) in the normal rat and newly appearing activities at pH 2.8 (inhibited by pepstatin) and pH 5.0 (not characterized) in the EAN rat. In EAN the proteolytic activity was not restricted to myelin substrate but degraded total sciatic nerve protein as well. Endogenous sciatic nerve protease at pH 5.8 did not significantly change in activity during the course of disease. On the contrary, activity of acid protease at pH 2.8 corresponded well to the disease. Myelin degradation in EAN, therefore, appears to be mainly due to exogenous non-tissue protease.