A lymph node neutral proteinase acting on myelin basic protein.

A neutral protease present in inguinal and popliteal lymph nodes of rats with acute experimental allergic encephalomyelitis (EAE), rats injected with Freund's adjuvant, and rats that are normal has been found to hydrolyze basic protein present in purified brain and spinal cord myelin. The enzyme has been enriched by ammonium sulfate precipitation, and its properties have been studied. The protease activity toward different substrates was very specific and decreased in the following order: Protamine sulfate = polylysine (MW 183,000) > myelin basic protein > histone > polylysine (MW 2000) > polyarginine > cytochrome c. Other proteins including casein, freshly denatured hemoglobin, egg albumin, bovine serum albumin, and ribonuclease were ineffective as substrates. The pH curve showed a peak at pH7 for rat myelin, isolated beef basic protein, and histone. A possible role for this enzyme in demyelination in acute experimental allergic encephalomyelitis is suggested.